A family member has property and wants to hold a mortgage to another family member for 15 years. They wanted to keep it in the seller's trust so that the buyer gets a stepped up basis. 

I don't know if you get a stepped up basis from a trust. I also don't know if his making payments (that are essentially market value) benefits from a stepped up basis. 

It seems that conveying the deed now with a purchase money mortgage is the way to go. 

Can I have your opinion please?