My in-laws want to sell me a building, recently appraised at 650K. 
The asking price is 500K.  They owe 130K.  I would like to purchase
the property from them using a conventional bank loan for the 130K and
owner financing for the remainder.

What is the best way to set up this transaction?  What are the rules
regarding this type of loan?  Is there a minimum interest rate that
must be charged?  Is it possible for them to 'gift' the property to me
and then have me gift back a payment every year to them, say 20K,
until the loan is repaid?