Help! Best way to structure home sale with family members

[David Gerber]

I'll provide the general situation but glad to share specifics via PM (and grateful for that!). Several moving parts and complex (at least for me), so bear with me:

Brother (J) owns home where mother (H) lives, has a cheap mortgage, but would like to extract his equity for other investments. H cannot afford to pay market rent so all members will subsidize in any case.

Grandmother (M) has cash that she'd like to leave to mother (H) and her brother (P).

Initial thought: M buys home from J, maybe with H&P for efficient estate planning (?), but leave mortgage in place. M pays J an agreed current value of his equity and then makes monthly mortgage payment to J (with assistance from others - M will contribute up to annual gift tax limitation). Assume in this scenario M can take mortgage interest deduction even though J will still hold the mortgage.

Is there a better way to structure this? THANK YOU for any advice. Again, PM me if specific numbers would help.