What documents do they require, what credit scores do they allow, how do they verify previous rental history, etc.?

Dead winter is not an ideal time to rent out a property so I expect it could take me 4-6 weeks or require discounting.

After we signed for the mortgage, he decided not to move in even though the conditions of the mortgage required him to do so.

If I’m selling a property to a retail buyer then of course I have the same requirements, even down to who the lender is. 

As long as I keep track of what expenses belong to which LLC, is it safe to continue running all of the payments and credit cards through the holdings company and then just divvy it up during tax time?

Looking at AirDNA results, my biggest concern is occupancy rates, most of the calendars I look at have large gaps in them, and when you spend close to $500/sq. ft at current prices (in STR-designated areas), your property needs to rent well above 80% or you charge crazy nightly rates.We've also seen very few property management companies that charge less than 25% there (and 25% is rare), and some STR neighborhoods require you to use their designated PM (Desert Colors only allows Red Rock, and they are at 40% commissions - ouch!).

Please be gentle; I'm new at this and it's pretty complex :)Structure / Legal Details- we'd establish market value through a combination of comps from local real estate agent and an appraisal- attorney would establish all required "arms length" aspects including a mortgage at a minimum standard federal rate- LLC would pay us back based on a standard promissory note over 30 yrs Pros of selling to the LLC (I think)- A sale now would be the only time we'd be able to take advantage of the cap gains exclusion on this house bc we won't qualify for the "live there 3 of 5 years" rule due to the timing of our lease and our last time of residence. 

and if you can't get approved for a conventional loan, you may be eligible for a DSCR loan.with that said... i am extremely skeptical that you can cash flow $500 a month including the debt service on the mortgage AND the HELOC plus all the expenses. 

I'm running into hangups with code section R302.3.1 which seemingly requires not only the floor separating the units to be fire rated but all the walls below supporting that floor to be fire rated (ie all exterior walls and load bearing interior walls on the first floor), which may mean extremely expensive fire rated windows at the lower unit.  

Many DSCR loans do not allow subordinate financing and will require downpayment funds to be sourced.