That’s a lot on one person
If just one person is taking on the mortgage, even though the other will make half the payments each month, that’s still a lot to ask of someone. If just one of you will be on the loan, that means just one of you, in the eyes of the lender, is on the hook for these payments, should anything go wrong—like him or you losing your job. As far as the paperwork is concerned, it’s just the person on that mortgage who needs to pay up. That’s a lot of stress for one person.