One potential con: Finding an assumable mortgage. I can't think of any lenders that are allowing assumable mortgages. I am sure there are some out there, but not many. But you said you could buy it from them, so no big deal.

On the same note, there are very few lease to own or rent to own properties available, and owners that will carry the financing typically want to see a good credit score.

Family transactions have a way of going bad, so while everyone is in good spirits about this, get everything in writing and make it a legally binding agreement. This will avoid misunderstandings down the road and keep everyone speaking at the family reunion.