Don't worry about that. If the tenants he chooses are also his housemates in the duplex he will quickly, in just a couple of tenants, learn to screen. He will also have the advantage of being there, so nothing much can go on that he's not aware of. Re fixing, between Home Depot and YouTube he's all set. You get to help, too.
+1
When she was a sophomore, we purchased a four bedroom house about 5 blocks from campus where DD attended college . We put her in charge of running the house--managing and paying expenses and operation as well as finding her roommates who would pay market rents. Most of the time she already knew the gals she rented to but by the time she graduated, she was having to screen and choose from people who heard she had space.
DD probably learned more about life and financial realities than she did from her university program. The house was a decent investment but value of her "learnings", at least match her classroom education---and the tenants paid for it! ;-)
