Depending on the size of the rooms, and what you want to do, a contractor will most likely average about $3K-$5k per room. 

And how much was the cost for an average IL winter?

Kind of like those teachers who felt like most of the class should get a "C" cause that is average kind of thing.  

Well... a lot has happened in 6 months. 6 months ago, units were selling for cheaper than they are today but it seems he just took an average.

You can also use some basic average costs of things like kitchens, bathrooms, roof, windows, flooring.

New listings have been below 2020 levels since the four-week period ending August 22.Active listings (the number of homes listed for sale at any point during the period) fell 21% from 2020.46% of homes that went under contract had an accepted offer within the first two weeks on the market, above the 43% rate of a year earlier.33% of homes that went under contract had an accepted offer within one week of hitting the market, up from 31% during the same period a year earlier.Homes that sold were on the market for a median of 20 days, up from the all-time low of 15 days seen in late June and July, and down from 32 days a year earlier.49% of homes sold above list price, up from 34% a year earlier.On average, 4.9% of homes for sale each week had a price drop, up 0.8 percentage points from the same time in 2020, and the highest level since the four-week period ending October 13, 2019.The average sale-to-list price ratio, which measures how close homes are selling to their asking prices, decreased to 101.2%.

My recommendation is to choose cities in safe and economically diversified areas with above-average income and population growth.

Something to do with the ratio of the average income of the individuals living there to the current growth of the population.

If you are using the freebie version of rentometer your single family home is probably being compared to apartments / multi-family comps which can skew down your average rents.

What is your average vacancy rate?