Structure shift (at least in my area) typically is caused by poor water management.

I was also going to suggest turning the water off from the inside. 

It is brick exterior with casement window and has water damage beside the windows (interior plaster is flaking/bulging).

(For example, upgrading water service or wiring or a new roof for the  entire building, a proportionate percentage of that should be a QRE toward the rental unit.)

You remediate the exact problem - mold comes from water leaks/intrusion - and forget about the rest of it.

The specific units I'm looking at are 1 BR/1 BA with a water view and poolsCan sleep anywhere from 2-6 with the addition of a pull out couch and a small bunk area for families$220K (Unrenovated) - $250K (Renovated) Similar units in the same building rented for $29K (this year) but "Closer to $36K in a stable year" (per management) My guesstimated costs will be $1500-2000 monthly using a 10% down vacation home loan, I'm considering using this management company at 26%The location is Tybee Island, Georgia.

If you can put mobile homes on your land, then you'll have to start figuring in costs to acquire the homes, pay for the move, and hook ups (i.e. water, electrical, gas, etc). 

My wife has stories of washing dishes using a large tub, and taking cold showers with water borrowed from our neighbor's hose, during the time our water was off to redo the plumbing!

Hiring tenants to do work has potential to muddy the water when things do work out according to plan. 

Ian Waters