The pieces interlock, are placed over a pad and/or vapor barrier and require a smooth, solid surface below for support.

It will take them Mon/Tuesday and Wednesday to get the sand, vapor barrier sheet and rebar in place.Plumber is supposed to come on site next week.

In the case of being highly leveraged when corrections occur and they will - your equity becomes vapor .I have 65% LTV overall on my portfolio and will be in the 60% range 12-31-2019.

I'll let your vaporous intimations of misconduct on my part pass without specific response.  

One contractor said moisture is coming through a hole in the exterior stucco, but another said no way because the vapor barrier would block it. 1st one recommended installing insulation, but I've also read this can increase condensation problems.

-No smoking, to include cigarettes, pipes, cigars, or any other tobacco smoking material, and/or vapor like products is allowed within the structure of the building; including the rental unit, basement, or garage, either by the Tenants or their guests.

An old garage slab will not have the correct steel, concrete PSI, or vapor barrier that is required nowadays.

Crawl space: have a vapor barrier and ventilation and no standing water (gutters and grading)Attics: no roof leaks and ventilationBasements: sump pumps are good and keep water away (gutters and grading) I don't love finished basements because you can't see if walls are taking in water.

3) Are insulation rolls with vapor barriors the most ecomical way to go?

You ALWAYS - no matter the floor want to put a vapor barrier between the underlayment and the floor material.