OR the alternative, take some appraisal courses and learn the methods. 

We have only purchased apartment complexes thus far (1,500+ units), but have strongly considered alternative investments like mobile home parks, as long as the numbers make sense.

As a 16 year old I don’t have the knowledge of what labor,materials, contractors, etc would cost.

With that you will be able to build out a project estimate, print out a report which will give you the market $ which is what you'd pay if hiring a GC, AND you can print off a cost report for same project seeing what material and labor costs should be, complete break down. 

People aren't going to see their dentists, optometrists, even primary care physicians, at least not enough to warrant demand from medical labs supplying tools, materials, supplies, etc. 

I bet that collections from the first through the sixth of March and April are materially closer than collections the first through the fifth.

Like most trades/services, the materials are cheap.

The house was built in 1940's and the material they've used is almost 2 inches thick with the tile.

Should I allow them do do this work themselves and pay the materials themselves? 

That helps build trust.Find alternative ways to communicate.