I made the house ADA friendly and the tenants have someone come in daily to cook and clean - they are great housemates. 

but 3+ plexes may have additional fire, ADA, parking, etc requirements. 

So, you need to think about zoning and then other things with which you may need to comply as a business (ADA access, restroom capacity, etc).

This makes my use of time very efficient as well as putting psychological pressure on the applicants to proceed immediately if they are at all interested.If they have not confirmed an hour prior to their appointment, I send this text to their phone (which was required as part of their contact information I required in the response to my ad):As I had requested in my email, you have not yet confirmed your apartment showing for this evening, scheduled for 7:00pm.

I think the site to look it up on is the ada.comMarci  Fair housing is different than ADA.

I have learned so far that HUD and the ADA have different assessments of ESAs and service animals. 

You can require return to prior condition even for ADA accommodation. 

@Deodat Ramdat so all in you'd be about 60K (I'd ad a buffer on this to be safe).

Considerations need to be made for possible additional stairways, elevator for ADA compliance and sprinklers.

The thing I think might come up is the ADA accommodations for the mom.