Yup, like sunrise pointed out, your partner's debt to income ratio would be too high to qualify for a $350k sales price on his own... it'd be over 70% and that doesn't qualify with any lender. You said that is your max though, what is more realistic for the sales price you'd be looking into? Is there any down payment involved?
Mom can co-sign though, but realize you don't want her too... I wouldn't really want to co-sign either, even for family. Too many risks to take with your own credit if their situation goes south.
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