My first Airbnb was a room in my house that brought in $1500 a month. 3 years later I have 7 Airbnbs that collectively bring in $12-14k.

I would recommend this rather than splitting the bill and trying to collect that amount each month. 

Anyone with a LT lease in place who has collected either two months rent or security and first months won't get tagged for vacancy. 

But here’s the thing to know about that deal: from execution of the PSA to collecting $1.7M took about 21 months.

Couple the two together and you have a receipt for tenants that cannot afford to live.As for trying to collect, you should ALWAY put them in collections for two reasons. 1.

I want to know if I buy a four plex under an FHA, claiming that one of the units will be my primary residence, can I move somebody into the unit I claim as my residence and collect rent from them without issue? 

You can invoice them monthly and collect like any other vendor. 

The due will be time/effort collecting.  

I want to purchase the properties, set up everyone on a month to month lease, transfer the utilities to tenants and eventually raise the rents and collect deposits. 1.

These areas have much more active management of properties with more collection issues, more turnover costs, more vacancy, etc.