Two story with downstairs the commercial?

I am currently looking at a property 1 in an area I'm sort of familiar with. property is  going for 130K 4bed/2baths and surrounding property are valued at around 100-222k it is off a mainstreet thats 5 mins away from the highway and shopping stores.

We built a kitchen, three bedrooms, and two bathrooms.

You could get cash out to build your basement unit and get two sets of new tenants.

I do like single family but, at the same time a duplex and up to a 4 unit seems more interesting.I look at this and wonder, if I plan to rehab one house, I’m better off working on a two units for the same effort of time it will take for just one unit single family.

For instance, if your property is listed for sale below its appraised value or if you reduce the asking price during the listing period, most lenders base their lending decisions on the lower of the two values.

Plus Dollywood is closed and it's just slower these two months. 

Every two years have them sale and move. 

Now here we are, and I’m just trying to figure out how to move from stage one to stage two.

As mentioned I am aware of the grandfathering if there were two previous structures meters but it looks like developers are buying RS-5s in a row and able to rezome multiple lots.I feel like years ago (5-8) there was a big stick about either R10 or RS10 lots but don’t have the info.Thought  I’d ask the hive mindThanks,Tim