If it has a separate entrance and isn't accessable within your dwelling (like renting rooms IN your SFH) You'll want it marked as a duplex for tax purposes, it's 2 units. 

I've owned my duplex for roughly 5 years, I am looking at renovating one of the bathrooms and front entrance to building for sure since they are in definite need of repair.

I would try to lay out the situation as best as possible to a lawyer that specializes in commercial leases in your area that can help you build out a template that you can tweak for the different type of tenant (retail, maker, storage).Things to keep in mind are hours they are allowed in or must be open, noise/music, exact responsibilities for anything that could be considered a liability (snow removal near their entrance, tripping hazards just outside their exact space, etc), specify their insurance requirements, etc.

The numbers I am giving you are for 1 camera to cover 6 storage units, plus special entrance/exit cameras.Cash Flow basis:Revenue- 170 equivalent units at say $80 each at 90% occupancy= $146,000 per year. 

Purchase price: $370,000 Cash invested: $2,500 Purchased a two-unit property (Technically an attached guesthouse w/ separate entrance and living space) in a market we specifically moved to based on the growth of the market.

Super states he sees 3 people other than the tenant staying in the unit and repeatedly using keys to gain entrance.

Each unit has roughly the same layout with the entrance to a dining room-living room with one bedroom branching off, leading to a small hallway with the bathroom and laundry closet leading to the kitchen, from which the second bedroom branches off.

I am also buying a single family house right now with a separate entrance to a mother-in-law apartment. 

There are rules with basements in terms of what qualifies as habitable (things like egress windows, possibly a separate entrance, and many other items I'm sure).

That's how we ended up converting the garage into a studio with a separate entrance from the main house.