I like the fact that one and a half units pays all bills.

See if you will have to pay for recapture.  

If your willing to do so, you can live in the casita and then rent out the main home and have your tenant pay the majority/all of the mortgage (depending on what type of deal you find obviously). 

I would stay away from section 8, pull credit and background, and call referrals, and look at pay stubs for everyone who applies.

Buyers don't look for financing and its foreign so they don't jump on a forsale listing on zillow.I've had the best (only) luck with zillow rental adds,   starting with the pitch;  rent to own, live in a great home while you pay off owning it. 

Google for a Service Agent who does Evictions and pay to get them out.

I use all the rental cash flow to pay these loans off asap, then repeat.

Or, if you pay 20k over list price on a property that is 50k underpriced, you still got a hell of a deal.

Then she still only makes 2% extra for taking the risk of you not paying versus a bank.

They didn't pay for it, so they don't take care of it like an owner.Before you make assumptions about costs based on a seller's contribution to improvements, find out what they improved?