It's basically a lifetime surface unless you damage it.

I pressure washed off the black moss on the brick in the back of the house and back patio along with all other concrete surfaces which made it look new.

Know that sometimes the roofs are not typical, 2 of mine did not have a plywood type of layer on the surface. 

If it it's more surface work, like painting, light fixtures, new cabinets, etc, you could likely accomplish it.The more likely scenario is that you have one really bad unit that you can start on either through terminating the lease or offering the tenants some kind of move off incentive.

@Keely AldingerOne other thing there is also primer stucco guys use to get stucco to adhere over painted surfaces.

Salting is also very rough to concrete surfaces, brick building masonry, etc.

The directions state for hard surfaces it can be diluted with 2 parts water to 1 product, and I suppose mop it on. 

With your background instead of buying turn-key, find something that maybe has some deferred maintenance and potentially some surface renovations (paint, tile, countertops, etc).

pool surface with modern material maybe 25 years (old plaster lasted longer than the newer surface material). 

You can learn a ton from youtube to help you with basic surface maintenance.