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Crunching costs, sorting signals, rendering insights.
Crunching costs, sorting signals, rendering insights.
The 30% rule — spending no more than 30% of gross income on housing — is the most widely cited benchmark for affordability. On a $40K salary, 0 cities (0%) meet this threshold. That's a tough market. We ran the numbers on 5 cities in Illinois using 2026 census, rent, and salary data. Rockford comes …
146,120 residents · Illinois
Real talk: Dive into Rockford's numbers: cost index 67 — which, honestly, is lower than you'd expect here — (44 points below national average), rent $1,151/month, income $53,328, and a home price of $172,610. The city's cost profile isn't flat — Housing is the cheapest category at 67, while Healthcare runs 93. With 146,120 residents, it balances mid-size city convenience with manageable costs.
150,489 residents · Illinois
Why Joliet ranks #2: the numbers tell a clear story. And depending on your situation, at 91 on the cost index, residents save roughly 20% less than the typical American. Rent sits at $1,559/month while the median household pulls in $88,026/year. The Housing category is particularly strong at 91, though Healthcare (98) lags behind. Home prices average $255,981 — $211,389 below the national median.
113,310 residents · Illinois
What does daily life actually cost in Elgin? Start with the 24% rent-to-income ratio — that's the kind of margin that lets people build savings. Fairly typical for a city this size. On the category level, Healthcare (index 100) is where the real savings show up, while Housing (index 101) is the line item most likely to surprise newcomers. Income at $88,316 — for better or worse — and homes at $323,259 round out a profile that ranks #3 for clear reasons.
150,245 residents · Illinois
Here's Naperville by the numbers — and there's a lot to like. And as a general rule, cost index: 126. Rent: $2,157/month. Income: $150,937/year. Home price: $594,498. Population: 150,245. The strongest category is Healthcare at 105; the most expensive is Housing at 126. Translate that rent to annual numbers, and residents are costing renters $3,144 more per year vs. the national median. This is an advantage that compounds over time.
2,664,452 residents · Illinois
At $2,292/month for rent and a cost index of 134, Chicago is pretty much what you'd expect from a larger city in this part of the country. Income is $75,134. It's fine. Not great, not bad (that's pre-tax, of course). The math checks out.
#1 Ranked: Rockford — cost index 67, rent $1,151/mo, income $53,328
0 of 5 cities keep rent under 30% of $40K
0 of 5 cities keep rent under 30% of $40K gross income
Data sourced from Census Bureau, Zillow, BLS, and Tax Foundation — current as of 2026
The 30% rule — spending no more than 30% of gross income on housing — is the most widely cited benchmark for affordability. On a $40K salary, 0 cities (0%) meet this threshold. That's a tough market. We ran the numbers on 5 cities in Illinois using 2026 census, rent, and salary data. Rockford comes out on top — here's the full ranking and analysis.
What does daily life actually cost in Rockford? Start with the 26% rent-to-income ratio — tight but manageable for most households. On the category level, Housing (index 67) is where the real savings show up, while Healthcare (index 93) is the line item most likely to surprise newcomers. Income at $53,328 and homes at $172,610 round out a profile that ranks #1 for clear reasons.
On a $40K salary, the key number is $1,000/month — that's 30% of gross, the standard affordability line. Rockford ($1,151/mo, 35%), Joliet ($1,559/mo, 47%), Elgin ($1,736/mo, 52%) all clear that bar. After federal tax, FICA (7.65%), and state income tax, estimated take-home ranges from $30,392 to $30,392/year across these top picks.
Here's where the story takes a turn: 0 of 5 cities keep rent under 30% of $40K. The 30% rule — spending no more than 30% of gross income on housing — is the most widely cited benchmark for affordability. On a $40K salary, 0 cities (0%) meet this threshold. That's a tough market. This is the type of edge you don't see advertised.
That said, Across Illinois, the average cost of living index is 104 — 7 points below the national median. Known for Chicago's premium versus downstate bargains, the state offers 5 tracked cities with median rents averaging $1,779/month. That's $116 less than the national average of $1,895. That's not a marginal difference — it reshapes your monthly budget.
Bottom line: Rockford leads this ranking for clear, data-backed reasons — but the "best" city depends on your priorities. Click into any city below to see the full detail page with 12-month trend charts, profession-specific salary data, and a breakdown of all five cost categories. If you're seriously considering a move, use our salary calculator to model your specific income against these numbers.
The 30% rule — spending no more than 30% of gross income on housing — is the most widely cited benchmark for affordability. On a $40K salary, 0 cities (0%) meet this threshold. That's a tough market.
#1-ranked Rockford has a cost index 37 points lower than the top-5 average of 104. That's not a marginal lead — it's a category of its own.
Rent ranges from $1,151/mo in Rockford to $2,292/mo in Chicago — a monthly difference of $1,141, or $13,692 per year.
Rent in #1-ranked Rockford has increased from $1,087 to $1,151/mo over the past 12 months — a 6% increase. Rising costs may erode its top ranking over time.
| City | State Tax | Sales Tax | Property Tax | Est. Take-Home |
|---|---|---|---|---|
1Rockford | 4.95% | 8.83% | 1.73% | $30,392 |
2Joliet | 4.95% | 8.83% | 1.73% | $30,392 |
3Elgin | 4.95% | 8.83% | 1.73% | $30,392 |
4Naperville | 4.95% | 8.83% | 1.73% | $30,392 |
5Chicago | 4.95% | 8.83% | 1.73% | $30,392 |
We model what a $40K salary looks like after taxes in each city: federal income tax (marginal brackets), FICA (7.65%), and state income tax. Then we compare take-home against local rent and costs to determine where the salary stretches furthest. All data is sourced from federal agencies and verified research institutions. Cost of living indices are normalized to 100 (national median) using Zillow rent as the primary signal, with sub-category adjustments derived from regional BLS price data. Rankings are updated monthly as new data is released.
Rockford ranks #1 in Illinois for this analysis with a cost index of 67 and median income of $53,328.
Yes. On a $40K salary in Rockford, rent would consume about 35% of your gross monthly income. Financial experts recommend keeping rent under 30%. It's tight — consider a roommate or nearby suburb.
Our cost of living index uses real Zillow rent data as the foundation, indexed to 100 (national median). Sub-categories (housing, food, transport, utilities, healthcare) are derived from the overall index with regional adjustments. Data is updated monthly.
Rockford (ranked #1) has a cost index of 67 and rent of $1,151/mo, while Chicago (ranked #5) has a cost index of 134 and rent of $2,292/mo — a 67-point difference in cost of living.
City data is refreshed monthly from Census Bureau population estimates, Zillow rent and home price indices, BLS salary data, and Tax Foundation tax rates. Last updated: 2026.
The median 1-bedroom rent in Rockford is $1,151/month as of 2026, based on Zillow's Observed Rent Index. This is $744 below the national median of $1,895/month.
After federal taxes, FICA (7.65%), and 4.95% state income tax, estimated take-home on $40K in Rockford is approximately $30,392/year ($2,533/month). After median rent of $1,151/month, you'd have roughly $16,580/year for all other expenses.
The median home price in Rockford is $172,610, which is 3.2× the local median income. That's within the standard 3.5× affordability rule for most local earners. The national median home price is $467,370.
Illinois has a 4.95% state income tax rate. Combined state and local sales tax averages 8.83%, and the effective property tax rate is 1.73%.
This ranking was generated using data current as of early 2026. Population and income data comes from the Census Bureau's American Community Survey (5-year estimates). Rent and home price data is from Zillow's monthly releases. Tax rates are from the Tax Foundation's 2025 edition. Rankings are refreshed monthly.