writing a note on home as a private lender

[Jay Jasunas]

I am selling a rental home to my tenant. He is getting a conventional 1st mortgage and is using all of his savings for the 10% down payment. He would like me to loan him $25k as a 2nd note the day after closing so he has some reserves, this is only 4% of the purchase price. 

I am thinking of structuring it as interest only with an 18 month term, he is good with that.

What would be the process I need to go thru to get this done? I don't want to screw with the sale, so is it best to contact the title company the day after closing to set up the promissory note and deed? How much would this typically cost?