They built the house in a way where someone could live in the bottom portion and then close off the inside stairway and split the bottom and top to turn the house into a duplex(there is outside stairs to lead up to the 2nd story).

Each has its own front/back door, for example, no interior access to the other unit (a stairway, for example), ...Then again, you do need to verify zoning, variances, etc.

(at present, the front hall is open, each "unit" has a separate locked door, stairway is open). 3.

Build two stairways: one in front, one in the backyard.

walls/windows/appliances. and a contractor stripping wallpaper in a stairway and dining room then texture and painting. replacing a door and know, replacing bathroom vanity mirror, some trash removal(tv)  it's all legit. 

if you plan to exit by selling it as a SFR definitely put in the interior stairway. 

I will be buying a spacious Duplex house, spacious kitchen and living room stair way up to three bedrooms with 1.5 baths, one full bath upstairs half next to kitchen (same for the next door). the person that had it almost finished the basement it is livable with nice ceramic bathroom, nice living room and potential for rooms. now i don't want to occupy these to make the most profit.

. $2,000 to replace a water heater... b/c the units were built with a gas hot water heater that was crammed under a tight stairway, don't really have enough airflow & now don't comply with code...

The first floor currently has hardwood floors and the stairway and upstairs are carpet.

Look for stairway cracks and signs of repair.Right now I am looking for homes on slabs.