I always replace toilets, shut off valves, water fixtures, add frostproof water spigots with additional isolation valves for winterizing, switches, light fixtures, Add ceiling fans to every bedroom, GFCI outlets, regular outlets, smoke detectors with 10-year or hard-wired-in, use a quality one coat semi-gloss paint, basic white washer/dryer and Exterior door locks with touchpads (key free). 

Additionally, the use of ceiling fans in these areas can further assist in distributing conditioned air more evenly throughout the house.

Im sure many of us have read all the warnings and reviews of buying low price properties, and the problems typically associated with them, but all that considered, it is what first attracts a lot of people , indeed this is the only path available to some, its a start, so lets explore whats real and possible.........lets use Detroit, Cleveland, Michigan and Indianapolis as examples where possible ,and set a ceiling of $30kPersonally i dont see the return on higher priced properties attractive enough to invest $80 to $120k plus, and before anyone starts preaching about the pitfalls, ive done this before, over 30 properties over 20 years, just in another country, low cost houses in deprived areas, i know what can go wrong.The first attraction here is the low cost, funding with personal loans and credit cards etc,  is possible, and with high returns , quickly repaid, whereas a large mortgage is on your credit file for years, and has to impact further borrowing, and cannot easily be cleared temporarily in the same way credit cards can, if your credit needs a boost !

Added new floors, new bathroom, new light fixtures and ceilings, created a bedroom from an office.What was the outcome?

Because my rents will remain at, or below market (even with the increases), and because my existing tenants are highly satisfied, I'm hopeful that the rent increases won't cause any tenant turnover...time will tell...One problem I may encounter is that rents in the broader market are currently pretty flat, so even though I'm currently below market, there may be a ceiling to how far I can increase.

Also it less expensive to fixed the mixed because the store is a shell with 4 walls, 1 ceiling 1 floor thats it besides the apartmenton the second floor.

This may involve installing drywall, flooring, and ceiling materials, as well as painting and decorating to your taste.

However, a cost segregation study may also report certain building occupancy items, such as carpeting, wall coverings, partitions, millwork, lighting fixtures, suspended ceilings, doors, as § 1245 property.

., an exposed ceiling in the laundry/utility room requires a drop ceiling - a city inspector would typically not require this but the housing authority will). 

there was a sag in in the Florida room, (now dining room) ceiling, so I HAD to poke it with a stick. three hours later half of the house was gutted.