Why your friendly local landlord is suddenly acting like a big-time robber baron

Ben Denzer for BI

Daniel doesn't think of himself as a mom-and-pop landlord. The 42-year-old engineer is a savvy real-estate investor, the kind of guy who scours the internet to find nearby rents and combs through new listings with an eye toward expanding his mini empire. He owns nearly 30 rental homes, and while he outsources their day-to-day management to a large company, he makes sure his properties are within a 1½ -hour drive of his Atlanta home so he can stop by if necessary.

Real-estate...