It seems like finding a better Property Manager is the step that needs to happen, and as one myself in MA, you just have to try again.  

I have experience managing this on multifamily properties as both an owner and a lender.

It seems like you have some very solid goals of multiple income streams, and a well calibrated risk tolerance. 

CIREA is great but we tent to get just as many people and a ton of great energy. rootsrealty.co/events 

I think I may have just answered my own question, but is it worth it to put only 10% down, and waiting for the equity to build to 20% in like a year and a half, or to bend over backwards, take out a loan and go in with 20% from the start?

I've worn three hats in the seller financing world (as a property buyer, as a property seller offering terms, and as an investor that buys seller financed note). 

I picked a mentor and a team to follow and the rest worked out

Quote from @Isadore Nelson: Give the expectation, a deadline, and a penalty.

If you want to nestle into North Scottsdale, you can get the big house and a decent lot, but it will not be a huge lot. 

I've also used traditional loans through regional banks and a few SBA loans.