Make sure you set up a separate entity for your long-term stuff (or even better an LLC for each property...) and one for flips if you end up doing any - that way there's no chance of being hit for self-employment tax as a 'dealer' under IRS code, for properties that you should have only been paying long-term capital gains tax, on sales of properties that you've held for over a year.

Are there any Chicago landlords out there familiar with smoke detector code in Illinois/Chicago? 

After taking a spin through the housing code, here is what I found: 1) houses built after 1987 have to be hardwired; and 2) houses built after 2011 have to be hardwired, and have a battery backup.

What may be required are things like getting a Certificate of Occupancy for the new units and inspections depending on local building codes.

My main priority is to get the place up to code.

., specific zip codes).

I would take the hit and find  licensed plumber and start entire process over and install "something" appropriate to local building code and obtain a fresh warranty. 

The codes, regulations and zoning are prohibitive.

What are y'all's thoughts on this zip code?

These will protect you and make sure the work is being done to code.