Investment Property in Illinois: 5 Costs Buyers Miss

What does an investment property really cost in Illinois?

An investment property in Illinois usually costs more to buy and hold than the listing suggests. Conventional loans sold to Fannie Mae require at least 15% down on a single-family rental and 25% on a 2-4 unit, plus six months of payments in reserve, and lenders count only 75% of the rent. The seller’s tax bill may also include exemptions you can’t keep, and Illinois landlord rules now apply even if you own one house.

By Kealan O’Neil | October 10, 2026

Most first-time investment property buyers in Chicago’s Western Suburbs start with the same math: the rent minus the mortgage equals profit. Then the real numbers show up. One first-time buyer asked Reddit what hidden costs they were missing in their rental analysis. In Chicago suburbs threads, rising property tax bills come up again and again.

I own and manage rentals here, so I run these numbers for my own portfolio, not only for clients. If you’re comparing a rental in Oswego, Yorkville, or Montgomery against keeping your money somewhere else, here are the five costs that change the answer most often. Get them right before you hire anyone or write an offer.

5 costs Fox Valley buyers miss on an investment property

1. The down payment and reserves are bigger than on your own home

Fannie Mae’s Eligibility Matrix (August 5, 2026 version) caps an investment property purchase at 85% loan-to-value for one unit and 75% for two to four units. That means at least 15% down on a single-family rental or townhome and 25% down on a duplex or fourplex. On your own home, the same matrix allows as much as 97% on one unit, with conditions.

Cash at closing is only part of it. For investment purchases underwritten through Fannie Mae’s Desktop Underwriter, the Selling Guide requires six months of reserves, measured as six times the new monthly payment including taxes, insurance, and any HOA dues. If you already own other financed properties, Fannie Mae adds reserves based on their loan balances, starting at 2% of the combined balance.

Pricing is different too. Fannie Mae applies a loan-level price adjustment to every investment property loan, which shows up as a higher rate or higher fees. Ask your lender for a quote on investment terms, not the owner-occupied rate you saw advertised.

There is one exception worth knowing. If you’ll live in one unit of a two- to four-unit building, the matrix treats it as your principal residence and allows up to 95% financing. That’s a very different deal from buying the same duplex as a pure rental.

2. Lenders count less rent than the lease says

Under Fannie Mae’s rule for rental income from the subject property (Selling Guide B3-3.8-02), a lender multiplies the monthly gross rent by 75%, then subtracts the full payment. The missing 25% covers vacancy and maintenance. If a house rents for $2,000, the lender counts $1,500.

Experience matters as well. If you have less than 12 months of property management history, positive rental income can only offset the new property’s payment. It can’t add to your qualifying income. For a first investment property, your own income has to carry more of the approval than most buyers expect.

I’d use the same haircut in your own investment property budget. Months between tenants, a furnace in January, and turnover cleaning are normal costs, not bad luck.

3. The seller’s tax bill isn’t the bill you’ll pay

Illinois gives a general homestead exemption only to a home occupied as the owner’s principal residence under 35 ILCS 200/15-175. In Kendall County, the Supervisor of Assessments lists the maximum reduction as $6,000 of equalized assessed value. Kane County, which borders Cook, lists $8,000. An investment property you don’t live in doesn’t get it.

The listing’s tax figure can also include a senior exemption, which Kendall County lists as a $5,000 reduction, or a senior assessment freeze. None of those transfer to you. To estimate the gap, multiply the exemptions shown on the bill by the local tax rate printed on that same bill.

The first bill can fool you, too. Under the same statute, the seller’s homestead exemption stays in effect for the rest of the assessment year of the sale outside Cook County. Your first tax bill may look fine, and the second one shows the real number. I cover the owner-occupied side in how the homestead exemption works, and if the assessment itself looks high, read my guide to a property tax appeal.

4. Illinois landlord rules apply to a single house

Many buyers assume landlord laws are for apartment buildings, not a single investment property. That changed. Since January 1, 2024, the Security Deposit Return Act applies to any lessor of residential property. If you keep any of a deposit for damage, you must send an itemized statement of the damage and repair costs, with receipts, within 30 days after the tenant moves out or the right to possession ends, whichever is later. Otherwise the full deposit is due within 45 days. If a landlord refuses to provide the statement or acts in bad faith and doesn’t return the deposit, a court can award twice the deposit, plus court costs and attorney’s fees.

Screening has rules as well. Since January 2023, the Illinois Human Rights Act has prohibited housing discrimination based on source of income, including Housing Choice Vouchers. According to the Illinois Department of Human Rights, you can require proof of income and apply a reasonable income standard, but you must apply it the same way to every applicant and count only the tenant’s share of the rent.

Town rules for an investment property vary, so check the specific address:

• Aurora: Every non-owner-occupied property must be registered with the city, with fees starting at $90 per property, and rentals are inspected every licensing year. Re-inspections start at $80, and a missed inspection costs $150.
• Oswego: Short-term rentals of 7 to 30 days need a special use permit from the Village Board, which the village says takes about three months, plus a $2,000 annual license, annual inspections, and $1,000,000 in liability coverage. Stays shorter than seven days aren’t allowed.
• Montgomery: The village’s code enforcement staff applies the 2021 International Property Maintenance Code and says it works with landlords on rental units. Ask village hall what applies before you close.

5. HOA leasing rules can shut the plan down

Many entry-level rentals in the Fox Valley are townhomes, and the supply is still growing. The final plat for Yorkville’s Grande Reserve Units 10B and 11B, for example, covers 154 new lots in the last stage of a planned townhome project, according to the city’s project page.

Before you buy a townhome or condo as an investment property, read the association’s declaration and rules for leasing limits. Under the Illinois Common Interest Community Association Act, an association can amend its declaration, bylaws, or rules to prohibit leasing through its amendment process, and the act also requires you to give the association a copy of each signed lease no later than occupancy or 10 days after signing. Some associations also cap rentals, set minimum terms, or charge fees. A leasing ban you find after closing can end the plan entirely, so ask for the declaration and rules before or during attorney review. If dues are already high, check for special assessments too.

Keeping your current home as an investment property

For many owners, the rental question starts with the house they’re moving out of. The question becomes: sell now, or keep it as an investment property and rent it out? The comparison is tax-heavy, so loop in your CPA.

Under IRS Publication 523, you can exclude up to $250,000 of gain, or $500,000 for a married couple filing jointly, if you owned and lived in the home for at least 24 months of the five years before the sale. In practice, if you move out and rent the home for more than three years, you can lose the exclusion. Depreciation also follows you: IRS Publication 527 sets the recovery period for residential rental buildings at 27.5 years, and Publication 523 says you can’t exclude the part of your gain equal to depreciation allowed or allowable after May 6, 1997. That includes depreciation you were entitled to take, even if you never claimed it.

Kendall County requires you to live in the home on January 1 of the assessment year to qualify for the homestead exemption, so once you move out, the rental loses it going forward. Call the assessment office when your use changes.

How to compare an investment property before you write an offer

This is the same sequence I use before I make an offer on a rental of my own.

1. Get a lender quote on investment terms. Confirm the down payment, reserves, and rate for a non-owner-occupied loan.
2. Rebuild the tax bill. Remove the homestead, senior, and freeze exemptions and apply the local rate.
3. Use 75% of market rent. Then subtract the full payment, including taxes, insurance, and HOA dues, plus a repair reserve.
4. Read the HOA documents. Look for leasing bans, caps, minimum terms, and fees.
5. Check the town. Ask about rental registration, inspections, and short-term rental rules for that address.
6. Plan your exit. Ask your CPA about depreciation, recapture, and the sale exclusion before you buy.

If the deal only works with the seller’s tax bill, full rent, and no vacancy, it doesn’t work. You can see the kinds of homes investors buy here on my page about investment properties in Kendall County.

Common questions about buying an investment property in the Fox Valley

These are the questions I hear most from buyers comparing their first rental.

Run the real numbers before you fall for the house

A good investment property in the Fox Valley still works after you add the larger down payment, the reserves, the real tax bill, and a realistic vacancy allowance. A weak one only works on the listing sheet.

If you’re weighing a rental in Oswego, Yorkville, Montgomery, or nearby, send me the address. I’ll put together a side-by-side comparison with the tax bill rebuilt without the seller’s exemptions, a rent range, HOA leasing rules, and town requirements, and I’ll connect you with a lender for a buying-power consult on investment terms. Call or text Kealan at 630-425-8815.

About Kealan O’Neil
Kealan O’Neil is the Designated Managing Broker and founder of O’Neil Property Group, an independent real estate brokerage based in Yorkville, Illinois. He and his team help buyers and sellers in Yorkville, Oswego, Montgomery, and the surrounding Kendall and Kane County communities, and he owns and manages a local rental portfolio, so he approaches every decision as both a broker and an investor. Call or text Kealan at 630-425-8815.

This post is general information about real estate in the Fox Valley, not legal, tax, or financial advice. Real estate laws, tax rules, and municipal ordinances change, and how they apply depends on your specific situation. Talk with a licensed attorney, CPA, or lender before making decisions about a purchase, sale, or tax matter. O’Neil Property Group is a licensed Illinois real estate brokerage.