They have gotten some nice improvements like a new patio, fenced in yard, new AC and all new light fixtures/ceiling fans. 

They may include painting the rooms for example but not to repair the plastic or to tape off the trim or scrape / clean walls.

It was built in 2006 and is mostly stone siding with a relatively small backyard, but a very large covered patio, big enough to watch football outside while it rains. 

The fan blade is relatively thin aluminum (older models) or plastic (newer), so don't go crazy when cleaning it.Tip: If you take the cover off, put the screws in your pocket, or put them in a plastic bag up on the kitchen counter. 

We have this property that we need to repair. Does anyone know what steps would be best to take or if it's better getting a pro in? Estimates on cost?

I have a tenant call and and said the weed wacker kicked up rocks and broke the glass to the  sliding patio door.

As I said, the house needs a lot of work. 1978 build with all original interior, floors were torn up, some foundation issues, pool needs replastering and the enclosed patio needs to be torn down. 

It's made from plastic milk/water bottles.

If so, parts of it have probably already been replaced with plastic (it rusts out). 

New electrical is better than real-old electrical with cloth insulation but not as good as 30-40 year old wiring with thicker copper wire and thicker plastic sheathing, so long as the sheathing isn't brittle.