Which will also depend on the neighborhood.You want to, "rehab/maintain to the Neighborhood".Most investors go overboard on their first rehab and waste a decent amount of money.

My opinion is a lack of business organization.

Neighborhood BThank you

For example, intro's to people here that can help you with certain specialties, planning, feedback on neighborhoods, financing of course, etc.

Look at recently sold properties in the same neighborhood that match the size, condition, and style your property will have post-rehab.

SPOA is an organization that I support. https://www.spoa.com/ Now I am very very careful when selecting tenants. 

.: I invest out of state in C-class neighborhoods in the Midwest.

What neighborhood of Chicago and how large are the buildings?

If you haven't already, try going off market, driving around neighborhoods that would be of interest to you and finding ones that fall into your criteria (your agent should be able to help you as well).

Start by exploring books, YouTube channels, market research, and analyzing trends in neighborhoods.