With 60 days notice, you may offer to transport them to another dwelling of their choice. 

The state requires at least one parking spot per dwelling unit.

IN DETERMINING WHETHER ALL OR PART OF THE RENT DUE AND OWING IS THE RESULT OF AN UNCONSCIONABLE RENT INCREASE, IT SHALL BE A REBUTTABLE PRESUMPTION THAT THE RENT FOR A DWELLING NOT PROTECTED BY RENT REGULATION IS UNCONSCIONABLE IF SAID RENT HAS BEEN INCREASED IN ANY CALENDAR YEAR BY A PERCENTAGE EXCEEDING ONE AND ONE-HALF TIMES THE ANNUAL PERCENTAGE CHANGE IN THE CONSUMER PRICE INDEX FOR THE REGION IN WHICH THE HOUSING ACCOMMODATION IS LOCATED, AS ESTABLISHED THE AUGUST PRECEDING THE CALENDAR YEAR IN QUESTION;"  This sounds like you can still increase rent but it will based on change in CPI for the area. 

If your partner puts a sign out up front where its visible then locals might change usage of property from residential dwelling to commercial business so keep that in mind..

An alternative would be to find a single-family home with enough square-footage to do a permitted accessory dwelling unit (ADU).

It's likely that the agent who owns this property can prove with a zoning certificate that it has 3 legal dwelling units, though it would ultimately be up to the buyer's due diligence to prove such. 

@Laura Blair - for the rocket lawyer contract template, searching for the term "ADU" or "accessory dwelling unit" doesn't seem to yield results.

Question is, is it worth the time/money to buy a single family home with a detached garage to turn into a ADU(additional dwelling unit) creating a 2 unit property.

Sherin,An umbrella policy provides a limit of liability above your homeowners, personal auto, dwelling/fire (aka Landlord policy), boat, motorcycle, ATV...The umbrella policy responds when the limit of the underlying policy such as the Homeowners is exhausted by a claim.

I think the hardest part of that would be finding a property with an ADU, but if you do I would reach out to the town/city hall on its rent-ability as a room or as an independent dwelling unit.