I feel like this is very state dependent. I'm in New York, Syracuse area specifically, and the city has been cracking down on investment owners the last few years, primarily aimed at reducing the amount of slumlords in the city. The process is an additional Codes inspection, and the certificates are good for 3 years, but must be renewed whenever the property is sold. Additionally, there is a push by local legislature to pass Good Cause eviction, which would further limit landlord power to evict tenant and terminate lease. I understand the intentions behind the goal, but implementation is a little questionable.
All is 'business as usual' her with the exception of vacation rentals that municipalities are waging war against this designation/usage due to the issues they can bring to their communities. Some cities have attempted to ban it and met with such strong opposition from the state (who loves the 'hotel tax' revenues from it) that they have made the inspection and construction requirements almost impossible for a property to meet the standard. It's been entertaining...will continue to be.