FHA loans are strictly for buying owner occupied property, not investments.

Always best not to invite further government regulation and interference into your business anyways.  

Each state has different regulations on how rents, security deposits and past months rents are to be handled.

Once you receive the deposit from your tenants, make sure you keep that money as restricted cash in your financial statement.It is ok to be in your bank account with other cash as long as your state regulation allows but you should properly keep it separate on your book to properly record it in terms of accounting.  

Private money is a very niche area that has fairly constantly changing regulations.

If are likely to have people with credit, savings, and/or stable incomes (social security or pensions) you can more easily enforce strict rules and penalties for late payments. 

As far as vacation rentals in Las Vegas - those are largely illegal now and if not illegal, very regulated. 

If its strictly a business relationship I would recommend him paying it to the title company or a loan servicing company.   

Dig in to the data, look at the occupancy, average daily rate, seasonality, regulations, etc.

(totally fixable,  but see point 1)5)   Increasingly complex, risky, and punitive seattle rental regulation ordinances already on the books6)   Winter Rent Control is coming.