As a matter of fact, arguably, it's less of a headache maintaining it.So with that said, I was wondering how feasible purchasing rentals would be in Milwaukee, Indiana, Chicago, etc. for 25 - 40k and renting them out with the intent of positive cash-flow.  

I recently picked up a copy of Professional Real Estate Development: The ULI Guide to the Business, 3rd Edition and I can't recommend it enough to anyone interested in becoming a real estate developer.It covers:How to get started in real estate developmentHow to analyze deals (market analysis, site selection, feasibility analysis, etc)How to finance deals (JV, commercial, private, syndication, govt programs, etc)Breakdown of how to develop residential, land, commercial, multifamily, officeAnalyzing real estate cyclesIncludes tons of case studies from all kinds of developersI really like the book because it is extremely practical and not just theoretical, even though the underlying rational is very academic in its approach.The book also makes a very strong emphasis on developers engaging the community as it is become more and more important to get community and political buy-in for successful projects.Definitely worth a read. 

Is it feasible to rent the units in their current condition? 

Why is it not required in any other city in the countryAnother interesting fact: Detroit paid a NY consulting firm for a feasibility study that looked at what it would cost for lead-based paint remediation and modern code compliance for an average Detroit SFR.

Now you let the lower wage scales do the dirty work of cleaning, repairing, painting and installing new fixtures and you no longer spend your more valuable time doing the low paying labor jobs, so now you can quite feasibly make $20,000 and spend $5,000 to do it.

With most solid properties going in a matter of days (or hours), it doesn't seem feasible to try and get 3-5 different contractors through the property for a bid before even making an offer.

What will be make or break feasibility wise for what you're proposing will be:Existing studs - nowadays max 16" O.C. spacing for 2x4 studs on 1st floor is required to carry a 2nd story and roof per 2015 IRC.Your existing truss system would save you a lot of $$$ if you can re-use. 

If an accessory apartment is located in the principal dwelling building, the entry to such unit andits design shall, to the degree reasonably feasible, reflect the appearance of the single-familyresidential structure.

Of those, it sounds like Panama City Beach may be the most feasible market.

I have heard up to 7 or 8 it should be fairly feasible if you buy the right properties.