If the building comes with tenants:
Make sure that the tenants are occupying the building as per the certificate of occupancy.
One to five family buildings are not typically rent stabilized, unless there is a tax abatement, in which case they may be.
Six and more families, typically are rent stabilized, depending on the rent range and history of the building.
Rent controlled tenants can exist in any older building and beware they are not all old people, rent control status can be inherited. So always ask how long the tenant has lived in the apartment and how did they come to be tenants.
The above are the basics, but make sure that you use a Real Estate lawyer that does regularly practice townhouse sales, rather than a co-op/condo Real Estate lawyer.
Going forward as to who and how you rent any vacancies; again make sure the certificate of occupancy is for the way the building is actually used; it is OK to rent out a combined unit ie: the lower two floors on the C of O reads as two floor throughs, but it is now used as a duplex is OK, but the reverse is absolutely a NO,NO!
A rent stabilized apartment needs to be rented or de-stabilized as per the rules governing such. (DHCR)
Please feel free to call if you need more help. I have over 30 years experience of managing and owning such buildings.
Kathryn Lilly, Broker
Realty on the Greene, LLC