A $400,000 house in Oak Brook carries about $4,400 a year in property taxes. The same house in Oak Park carries about $11,600.
That is a $600 monthly difference, and it is larger than anything a quarter-point move in your mortgage rate will do to you. It is also the variable the standard rent-versus-buy calculator never asks about. It wants your rate, your down payment, and your time horizon; out here the county line moves the answer more than any of the three.
The numbers below were checked July 30, 2026; the mortgage rate was re-checked August 15.
On this page: What Each Choice Costs · Today's Numbers · The County Question · One Worked Example, Not a Universal Claim · The Costs Nobody Quotes You · Help With the Down Payment · How to Use This · Rent If, Buy If
What Each Choice Costs
| Renting | Buying | |
|---|---|---|
| Upfront cash | First month plus deposit, typically under $5,000 | Down payment plus closing costs, commonly 2%–5% of price by lender estimate, plus transfer stamps |
| Monthly carrying cost | One number, fixed for the lease term | Mortgage, property tax, insurance, and whatever breaks |
| Flexibility | Leave at lease end | Selling costs real money and takes real time |
| Tax exposure | The landlord's problem, passed through at renewal | Yours, and it can be reassessed upward while you do nothing |
| Maintenance risk | The landlord's | Yours, unbudgeted and badly timed |
| When it usually wins | Horizons under about five years | Horizons past about five years, if the monthly works |
The five-year line is a rule of thumb rather than a law. It's roughly where the transaction costs of buying and then selling — stamps, fees, commissions — stop swamping whatever equity and appreciation you've built. Your own line moves with your rate, your tax bill, and how long you stay, which is usually shorter than you think when you sign.
Today's Numbers
The rate. Freddie Mac's weekly survey put the 30-year fixed at 6.67% and the 15-year at 5.96% for the week ending August 13, 2026. It climbed through July, from 6.43% at the start of the month to 6.66% at the end, peaked at 6.69% the week after that, and has just ticked back down.
Prices. The Chicago-metro median sale price was $407,000 in June 2026, up 4.6% year over year, on 9,927 closed sales. If you have read that the suburbs sit in the $350,000s, that figure is more than a year stale.
Inventory. The nine-county metro had 14,992 homes for sale in June, down 14.4% from a year earlier.
The statewide picture is tighter than most people realize, and it is checkable. Realtor.com publishes an active-listing count for every state each month. Illinois had 19,210 active listings in June 2026 against 54,100 in June 2019 — about 35% of the pre-pandemic level. Running that same June-to-June comparison across all fifty states puts Illinois second from the bottom: only Connecticut is tighter, at 29%. Third place, New Jersey, sits at 43%, a long way up from where we are.
Thin supply is why buyers here compete on terms — waived contingencies, flexible closings — rather than on price, and why "wait for more listings" has been bad advice in this market for four years running.
Rents. These come from listing aggregators rather than a government source, and they disagree because they measure different things. Zumper puts a Chicago one-bedroom at $2,162 and a two-bedroom at $2,500 as of July 30, both down slightly year over year. RentCafe, which counts only buildings of 50 or more units, reports $2,454 and $3,295 — the higher figures follow from the bigger, newer buildings its methodology selects for. Suburban asking rents generally run below the city numbers.
The County Question
Effective tax rates — the bill as a percentage of market value — vary more within Illinois counties than between them.
Using the Civic Federation's estimated effective rates for tax year 2022, the most recent edition published:
| County | Sample low | Sample high |
|---|---|---|
| Cook (residential) | Chicago 1.69%, Glenview 1.83% | Oak Park 2.89%, Chicago Heights 3.24%, Harvey 4.74% |
| DuPage | Oak Brook 1.09%, Naperville 1.81% | Wheaton 1.96% |
| Lake | Lake Forest 1.68% | Waukegan 2.62%, Buffalo Grove 2.72% |
Two conclusions follow. "DuPage is the expensive one" is folklore — the DuPage towns sampled here run below most of Cook's suburban municipalities. And the spread inside Cook is wider than the spread between counties: on a $400,000 house, Glenview's rate produces about $7,300 a year while Oak Park's produces about $11,600.
Cook has a further wrinkle to understand before you buy there. It assesses residential and commercial property differently, reassessment can move your bill without any action by you, and the second-installment bills are late again this year. The county announced on June 9 that they would be delayed by approximately two months; that announcement named no mailing or due date, and the Treasurer still had not posted one as of mid-August. If you're buying in Cook this fall, the bill you're prorating at closing may not exist yet.
We've written up what each line on the Cook bill means and how to appeal it, and which suburbs carry the lowest rates is its own guide.
One Worked Example, Not a Universal Claim
The arithmetic below is for one hypothetical buyer, shown so you can substitute your own inputs. It is not a recommendation.
A $400,000 house, 10% down ($40,000), 30-year fixed at 6.67%, in a town with a 2.0% effective rate:
| Line | Monthly |
|---|---|
| Principal and interest on $360,000 | ~$2,316 |
| Property tax at 2.0% of value | ~$667 |
| Homeowners insurance (private estimates, $2,400–$3,000/yr) | ~$200–$250 |
| Before maintenance, PMI, or HOA | ~$3,185–$3,235 |
Against a suburban two-bedroom asking somewhere between $1,800 and $2,500, the monthly gap is real, and the tax line alone exceeds what most people budget for it.
Now move that identical house. At Oak Brook's 1.09% the tax line falls to about $363 a month. At Oak Park's 2.89% it rises to about $963 — a $600 monthly swing driven by nothing but the address, on the same house at the same rate with the same money down.
What the example leaves out: PMI, which applies below 20% down; HOA dues; the transfer stamps below; closing costs; and the money you will spend on the house in year one. Run it again with your own inputs before it means anything.
The Costs Nobody Quotes You
Transfer taxes. Illinois charges $0.50 per $500 of value at the state level and $0.25 per $500 at the county level. Then the municipality adds its own, and both the rate and which party pays vary by village. Naperville charges $1.50 per $500 and requires the buyer to purchase the stamp by city ordinance. Evanston charges $5 per $1,000 up to $1.5 million and puts it on the seller unless the contract says otherwise, rising to $7 and then $9 per $1,000 in higher tiers. Two towns twenty miles apart, opposite sides of the table. Check the village's own page rather than assuming.
Closing costs. No government body publishes an Illinois average. Lender and brokerage estimates cluster at 2% to 5% of purchase price, a range wide enough that only your own lender's written estimate is any use.
Insurance. Premiums have risen sharply in Illinois over the past several years. The commonly cited averages, from $2,400 to over $3,000, are private estimates that vary by methodology, so treat the line in the table above as a placeholder until you have a real quote on a real address.
Help With the Down Payment
IHDA offers four assistance programs, all requiring you to occupy the home as your primary residence:
- IHDAccess Home — 6% of purchase price up to $15,000, deferred, no monthly payment.
- IHDAccess Repayable — 10% up to $10,000, repaid monthly over ten years.
- IHDAccess Deferred — 5% up to $7,500, deferred.
- IHDAccess Forgivable — 4% up to $6,000, forgiven over ten years.
Eligibility runs on county-specific income and purchase-price limits, set by the county where the house is rather than where you live now. Those tables change, so read them on IHDA's own limits page.
One correction, because it is still being recommended: SmartBuy is closed. It stopped taking reservations on February 24, 2025, after demand exhausted the funding in under three months. Only previously locked files remain funded.
How to Use This
1. Get the parcel's tax number, not the county average — look up the most recent bill by PIN. The listing's tax figure may predate a reassessment. 2. Find the village's transfer tax and who pays it. That's a four-figure surprise in some towns. 3. Price the same house in two counties if your search crosses a line. The tax difference is a bigger lever than a quarter-point on your rate. 4. Be honest about the horizon. Under five years, transaction costs usually eat the case for buying. 5. Then compare monthlies — full carrying cost against real asking rents, not the mortgage payment alone.
Takeaway: in the Chicago suburbs the deciding variable usually isn't the mortgage rate, it's the parcel's tax bill and how long you'll stay. Two identical houses, one at 1.09% and one at 2.89%, differ by roughly $600 a month before anyone mentions interest.
Rent If, Buy If
Rent if you might move within five years; you can't cover the down payment plus 2%–5% closing costs without draining your reserves; your search crosses county lines and you haven't priced the tax difference yet; or you'd be buying at the top of your budget in a high-rate town, where a reassessment is a real risk to your monthly.
Buy if you're staying past five years and the full carrying cost clears comfortably; you qualify for IHDA assistance that closes the down-payment gap; or you've found a lower-rate town where the tax math works in your favor for the long haul.
To run your own numbers, the rent vs. buy calculator compares a monthly mortgage-plus-tax payment against the rent you'd pay instead.
Sources checked July 30, 2026 (mortgage rate re-checked August 12): Freddie Mac Primary Mortgage Market Survey (week ending 08/06/2026); Illinois REALTORS June 2026 market report; Realtor.com active-listing counts for all fifty states via FRED, June 2019 and June 2026; Civic Federation estimated effective property tax rates, tax year 2022; Illinois Department of Revenue and county transfer-tax schedules; City of Naperville and City of Evanston transfer-tax pages; IHDA program directory; Cook County's June 9, 2026 announcement on delayed second-installment bills. Rent figures are listing-aggregator data from Zumper and RentCafe and are labeled as such above.
This guide is part of The First-Time Buyer's Suburban Starter Pack.