When Tylisha Slaughter learned that the West Philadelphia rowhouse she rented was going to be auctioned off in a sheriff’s sale, she sensed opportunity. Slaughter, now 30, aimed to buy the home near Cobbs Creek Park on the cheap and restore it from the “slumlord”-like conditions she, her boyfriend, and her two young children had been living in. But on the day of the sale, she said, she found herself up against an out-of-towner with lots of money to spend: Brandon “Dutch” Mendenhall. “He outbid me,” said Slaughter, whose rent has risen from $700 to $900 since Mendenhall’s RAD Diversified REIT became her new landlord in late 2019, even as…