Kurt's comment about checking costs of competitive housing solutions is very important. There are areas of Illinois where owning a community is a real struggle unless you just want to own the local slum.
Skip western Illinois and South of Interstate 72 unless you want low end communities, with the obvious exception of the Metro East area on the Illinois side of St. Louis. You can make real money in Metro, but the regulators and the liberal judges will make it less fun.
Sangamon County is a great area to own communities because home ownership is high enough to make owning a manufactured home sited in a land lease community a bargain at a number of price points. Local regulators are also very easy to deal with.
The counties to the South and West of Cook County have been gold mines for many years, especially for larger operators.
Champaign County is also a gold mine area but again you will be dealing with anti business politicians and judges. The Bloomington-Normal area is also a very good area, but local regulators are tough. Peoria County also offers opportunity with less government regulation and better judges.