You should search out your state landlord tenant regulations on line.

We're interested in doing more townhouses and condos (strictly because of affordability).  

Rental properties have a higher standard for dryer venting,, most city inspectors will require you to have smooth sheet metal duct, not any of the accordion type dryer vent hoses made of plastic or flexi metal.. and must be vented outside..I'd call city talk to inspection department and find out the regulations.. as your currently "thinking" about adding a dryer... honestly we had a huge issue with trying to install a washer and dryer in a 4 plex,, the city inspector would not permit use because we didn't have a egress window in the basement for an additional way to exit,, code required 2 exits out of basement to have a washer or dryer for use.. basically the basement was off limits. because of no 2nd point of exit we couldn't even let tenant's down there so we had to lock it off. 

You need to take the time to sit down and study your state landlord tenant regulations.

Does that violate regulations with the state?

The fact that I'm going to get 17.5% ROI strictly on the cash purchase (Rent / Purchase Price)2.

For this to be implemented it would need to be regulated very strongly which means the US government would need to write up the regulations.

This is illegal and highly regulated.

Im locates in New Jersey so I’ll have to look up the regulations here.

You can typically pay someone like that a strict percentage number.