Being out three months of rent plus $1,500, I'd be better off handing back their SD and forgiving the month of rent they couldn't pay.  

In return, they will be motivated to get a job and pay back every dime owed while lavishing you with praise.

Just sell and pay off that loan or two.

Ignore the $1,250 per month because that's your cost of housing, if you didn't pay that on the home you'd have paid that in rent so that's a non factor. 

What would I need to do to structure the note in order to have a note buyer come in and buy the note or buy a partial enough to pay off the 215k at closing and still have some difference coming to me or the note revert back to me after the partial was paid for. 

That will increase your material costs for the job and is the contractor paying for the material in their bid or are you paying for it and paying them a labor cost.

Some PMC's will charge a lower percentage fee, but will charge it whether tenant paying or not.

More than happy to partner up or pay for the deal itself.

One would think that a bidder would pay $45,000 in my example (since they are assuming the first mortgage), but they are actually bidding $225,000.

I noticed that the previous owner let them pay half the security deposit and the other half later, which is a red flag.