There is enough space to do so, and there is a separate entrance to the backyard.

(My duplex has common building entrance and then separate apt entrances.

I house-hacked a single-family home that had separate entrances; this allowed for the comfortability of living with privacy while also getting the benefit of rental income and qualifies you for the perks of owner-occupied loans.

I have recently been divorced and my ex and I co-own a 2000+sqft, 3br, 2.5 ba, 0.75 acer property with an additional 16x25 office space that has its own exterior entrance/exit and 0.5 bath, and a large one car garage.

If the current property is not zoned for two family housing, locals can tell you if rezoning is possible, but I would bet it would be very difficult to get approval.Next, you will need to separate the units, which will mean separate entrance, complete separate spaces, and most likely the city/county will make you separate the units with the current code fire partition, which generally is a 1hr rated wall/ceiling (which can be done with 5/8" fire rated drywall on each side of solid 2x framing).If you are not rewiring, replumbing, etc, then you would most likely be stuck paying for the utilities, which sucks. 

That being said, we purchased a SFR with an unfinished basement that had an exterior entrance only that we are now converting into a separate living space, effectively making it a duplex.

This unit is separately metered and has 6 units with 6 entrances and 6 paying tenants.  

I just put in an offer for a buyer for an Englewood home, one block off Broadway with a totally updated basement apartment with a separate entrance and everything.

There's an exterior door in the back that serves as a separate entrance to the back.The building is listed for $395k which is in the ballpark of correct pricing for the home.  

They added an uneven facade (which you couldn't do due to roof line) , different colors, 2'x6" for privacy for each entrance and bamboo in front, as well as other landscaping.