People are missing out on the fact that it's in HIS name, not the Mom's. Heck, I'd suggest that the MOM get everything in writing so that she doesn't get evicted! I don't think the OP is the type but elderly abuse and kids taking parents to the cleaners before their death is not uncommon.
In answer to the question, I think it's a good tradeoff in general, and not only financial. You are getting a house half paid for in return for no cashflow but all of the appreciation at her death.
I'm assuming that she will pay for tax and insurance? Or will you be?
In the end, not all calculations are financial.