Actually, in Florida, the property must be in at least one of the spouses' names. If you put it in the name of the husband's mother, I don't think it's protected. But the wife should know better than to let the property be in the husband's mother's name--and so should the husband! If it's in the husband's name, everything is fine.
It wouldn't be protected if the property was in the husband's mothers name but I've yet to see a mortgage company give what would be tatamount to a non-secured note so the mother would be the one also qualifying for the loan. A cash transaction I could see or where the mother is buying the property for the kids to live in but not where the spouse is the purchaser with loan proceeds. In that case both spouses must sign the mortgage.