I'm splitting the cost with the neighbor.)Interior: Tile the hallway/kitchen/bathrooms, put in basic stove/fridge (nothing more), install new drywall in the kitchen/dining room, and apply fresh paint.I want to do a bit more such as replacing the cabinet doors (I'd go with flat-panels), replacing light fixtures in the dining room, and putting in faux wood blinds.

This home is about 1600 sq. ft, 2/1 double carport, with formal dining, converted garage family room, and den.

We paid market value and did some minor work (diy kitchen reno, converted bedroom to formal dining, new flooring in partially finished basement, landscaping). 1 year later we split up and I still reside in the house.

Here is an example: Lets say I buy a typical 2400-3000 s.f. home in a desirable neigborhood in my local area that was built in the 1990's and has the typical builder-grade finishes of that era (plain oak cabinets, formica countertops, wall-to-wall carpeting in the living and dining rooms, plain 4 x 4 tiles in the bath--you know the type--serviceable buy "dated"--we have LOTS of them around here!) 

The room right off of the kitchen, is that a dining room or a family room? 

I would totally get rid of those cabinets that have been stuck in over the "pass through" to the dining room.

it was at that point I realized that the person on the lease was only supposed to be paying 800 a month for a 3br house, she charged rent to all the other rooms in the house, including the living room and dining room which she turned in to bedrooms.  

I would never consider buying a couch, dining room set, or even a permanent shrub for the house without asking my wife's permission and input. 

By common areas, I am referring to the living/dining/kitchen/hallways.

That quote included the bathroom fan/light combo, smoke detectors, outlets & switches, as well as the can lights.We had to provide the ceiling fans, bathroom light fixtures, dining room light, and counter pendant lights.