I’d like to finance the property to someone who maybe can’t qualify for a conventional loan and secure a loan for them at slightly above or at the market interest rate.Does anyone know how to go about doing this from a legal/underwriting perspective?

I actually don't know if there is any reported case law on this, but it would be stupid for a court to hold that the landlord is in breach in such a situation. 

The tenants’ security deposits should transfer to the new owner (you in this case) because you’ll ultimately be responsible for returning them to the tenants when they move out.

Should I just keep the security deposit as last months rent and let it go?

I've ordered new security lights and will get those up, hopefully before new people move in, and will likely install cameras as well (perhaps not if I put the fence up).

They even said they would let us secure a tenet in there before we owed then the 90 grand.

I love that they are all owned free and clear, that Is true financial security right now.

.), you should require a nonrefundable earnest money deposit.Having the buyer furnish an nonrefundable earnest money deposit secures your position in making a profit.

You should probably open 2, one for expenses and one for security deposits.

Of course you can also go the personal route to secure 30 year fixed financing, then transfer into the LLC.