Rently has been working for me its pretty simple, the only Issue I had was with stupid people not following directions when putting in the code to open the lockbox, but I was able to walk them through it on the phone.

Which one (usually, and I understand it's not simple) has a better resale and long-term potential?

This is where a simple, old school paper application/word document will serve you well. 

Plain and simple.

Simple answer networking, I can get as many as I want in my market.

Something simple and low work, instead of a rehab, to get my feet wet without too much risk?

I suspect a simple search of public records would show who they are .. there cant be that many companies with 150 plus SFRs in that market ?? 

That process is simple obviously.

RE is nothing but math, just know your numbers ,Buy right, reno right, rent/ sell right, YES that simple LOL 

If you are able to succeed at this, you could make a lot of money in 10-12 after holding these properties.The formula is simple.