Need Advise please, buying house 80%/20%

[Keith Perkins]

Wife and I have planned on turning our home into a rental but a member of our church is moving to Florida and has not signed with a realtor yet and will be selling their home. This is a couple of years ahead of our schedule because we have not saved the 20% down for the down payment on the new home. We have the money in retirement accounts but really did not want to do that. My solution is offer the homeowner their full asking price if they allow us to do a conventional 80% loan and seller financing the the 20% needed to stay away from paying PMI. I will add that we really like the neighborhood they live in and have been planning to look in their anyways and it is also 5 minutes from my mother in-law's which has several benefits as well. So assuming they agree, how do I make it legal and will it apply to our overall DTI (the 20%). I do appreciate any help or suggestions.