That would be a bank/risk decision.
Is the bank assuming that he will be moving and encurring additional expenses? /or/ is he OK living with mom & dad? You may want to make your assumption based on applicant's response, and use it in all cases. This may include still in school and living in a dorm; moving in with friends (or boy/girl friend), just relocated and staying with relatives for the time being, etc.
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Integrity. With it, nothing else matters. Without it, nothing else matters.