They moved in on November 15th so I have recieved $2,000 (deposit) and $800 (prorated rent). 

I'm assuming you want to grow your portfolio.....don't start off by on the wrong foot with a Housing Authority. 2)   Get as large of a security deposit as possible.    

My rentals(6 doors across 2 properties) have a bank account for Sec deposits and then an operating account.

@Cathy MalmroseAll else aside, your son is essentially a landlord for this time and he could put together a lease agreement immediately (ideally with the help of an attorney), which outlines a security deposit in case of damages, requires the prior owner to obtain renters insurance, who pays utilities and any daily rent- especially a daily amount that’s high if they stay beyond a certain date.This would at least cover the primary points in a leaseback.I’m curious about when and how the sellers made the request to stay past closing that your son agreed to - was it just between the two parties or was the Realtor part of that conversation?

Some people say you need an account for each rental for the deposit, but you don't where I am. 

The vast majority of lawsuits against Landlords are for wrongful eviction, security deposit disputes, and Fair Housing Violations.

Think of all the things that could go wrong and see if the lease addresses them: unauthorized pets or tenants, early termination, security deposit, lease violations, late rent, eviction, lawn maintenance, parking, etc.5.

Every deposit is revenue. 

Graciously we agreed and drafted a letter of intent which is currently on file and bound by a $1k Deposit.

If your currently builder doesn’t offer any internal services to transition you, you could: - Borrow agains you IRA (401k), depending on the cost of the deposit, and pay it back when your old home sales and it's off the market.- Use a HELOC (80% - 85% of appraised values of current home) to use as deposit for the construction loan requirements (10% - 30%) and the debt would be concluded during the sale of the home.- Gift from family member as a deposit, and payback when the home salesThe question is really broad, so if I have misunderstood you question please let me know.