Just my .02, I'm not sure about specific laws in Chicago, but I completed a 203k for my first Duplex since trying to find good deals in my area was really competitive. All in all I had a positive experience and this is what I learned from the process.
1. ONLY go through a lender that has done many 203k loans
2. Contractor doesn't need to be 203k certified, but has to fill out contractor packet, W-9, have HIC License, and carry a minimum of $1 million liability policy and have the lender listed as the certificate holder on the policy (not $500k) which cost me an other week to correct during closing.
3. Streamline is up to $35k with no structural repairs, the full requires a consultant. My project was a full gut and we had to fix a part of the foundation, and cost about $90k and took 3.5 months to complete. I bought it for $151k, reno was 90k, and the house appraised at $300k. This gave me $60k in equity right off the bat and I practically have a new construction house, so it's also low maintenance.
4. The loan is a major PITA, and will take 3 months to close, so plan accordingly so you don't need an extension. If you're able to deal with the headache I'm an advocate for it. Now I'll never do another one now that I'm looking for future deals, but I truly believe I never would have gotten started or would have no equity and low cashflow like many other investors in my area.
That's just the tip of the iceberg, and it is complicated, but definatly not as impossible as everyone (thats never tried one) make it out to be. If you don't mind the bumpy ride, then I strongly suggest looking in to it and would love to answer any questions on it if you have any.
Here's a couple photos to show you what's possible, for $17k out of pocket for a $300k house, it's definitely a great way to get creative.
I have many more if you're interested. Good Luck- Erik