Legal Question in Real Estate Law in New York

I am answering on the basis of what you asked, but this is a very weird situation.

In order for a person to "be on the mortgage" that person has to own the property. If the mortgage is in the son's name alone, then said son will be the sole owner of the house. If mother and father sign the note (i.e. make the payments) then each and every mortgage payment (including tax and insurance) will be treated as a gift to the other son. And the tax consequences of that kind of gift program are staggering. Gifts in excess of $10,000 per year trigger gift tax, which is payable by the person GIVING the gift, not the one receiving it. And in the event of a divorce, the other son already has title to the house so there's nothing to divide.

I would seriously counsel mother to smell the coffee. There is absolutely nothing good about this plan. It announces an intent on husband's part to separate mother from her assets/