Your question is very broad, maybe you could narrow your scope a bit?

If you buy right and have the cash reserves then you should in theory be fine.But if your planning on using tenant A's rent to pay the mortgage of tenant b and c ....and live paycheck to paycheck might want to rethink the approach.

I will have to get each unit ready and stage the work, so while I get the unit A ready, I can't be turning over B and C.Susan and Joy are not looking to be roommates, at least that's the impression I got. 

As far as real estate, start with a general book like mine to figure out what direction you want to go and then you can narrow in on that specific area.

I’ve narrow my search a lot.

If you can narrow your region a bit, that may help you get more bang for your buck.

I think it rally depends on your strategy, if you are after capital growth, cash-flow or Air B and B.

Might be state specific, but in general it would only be lawful for the real estate agent to pay you hourly or salary, and the scope of what you can do without crossing the line into "selling" real estate without a license will be a very narrow one.If you want to be the real estate agent, then I'd suggest getting your real estate agent license.... think of the dumbest real estate agent you've ever met: if that person can pass the little test, you can certainly pass it too right? 

There are many things to factor in such as customer service, speed of transactions, general knowledge and also the fees (annual and transactions).Check out the bigger pockets list of self-directed custodians.https://www.biggerpockets.com/rei/self-directed-ir...I would recommend you narrow it down to your top 3 and call each one.

I wholeheartedly agree with @Bob B. and will take it a step further and say find a financial adviser who does it for a fee, not a commission.