Either way could work. He could even do both. Buy a multi-family, rent out the other units long term. In the short term while he is still young and single he could also rent out the additional rooms in the unit he occupies his friends… This could allow him to super-charge his cash flow… If/when he decides to get married or settle down (which could be 10 plus years away) he could decide to get rid of the roommates in his unit or move out altogether

turn that property into a pure rental property and find a new living siutation.