Son is "purchasing" a home from Mom and Dad. Son already lives in the house as his primary residence. He is already on the deed as an owner of the dwelling along with Mom and Dad. However, he is now officially purchasing the home. There is a sales contract. Son will pay state tax stamps and a warranty deed will be completed to remove mom and dad.

We are treating this as a purchase for TRID, but wouldn't Right of Rescission apply since he is already a owner of the dwelling?

From your description - yes. He has ownership interest in the property and it's his primary residence.

agreed.

This is not, IMHO, a purchase...it could be a cash out equity to buy out full interest or it could be a cash out refi for same purposed if there is an outstanding debt...but not a purchase as he already has ownership.

ROR would apply, regardless of what you call it.

for TRID, he already has an ownership in the 'dirt' so purchase just does not compute.

Think about the scenario where a person owns the dirt, but is purchasing a MH to place on it.

Purchase for HMDA, but Home Equity for TRID.