Taxes in Chicago have gone up, but like @Josh Kundrat said, it's at least comparable to other surrounding areas. I know of many suburbs that have wayyy higher taxes.
Taxes are included in your PITI calculation "principal, interest, taxes, insurance." It should be calculated into your net cash flow because these will be outgoing payments, among other things. You can try to estimate increases in taxes going forward, but sometimes that can be difficult because it's based on assumptions. Factor in some of the local regulations being mentioned and look at it like... how much could taxes increase in order for me to still make my minimum net cash flow requirement per month. If taxes going up even a little bit would make the deal not worth it, then maybe don't purchase.
Analysis points could include:
-Average days on market
-Saturation rate
-Median sales price
-Inventory of homes for sale
-Percent of original list price received
-Change in median sales price
compare this month to last month, but also year-over-year, winter markets tend to slow down so it's not really "fair" to compare it solely to the summer.