I have a guy who does a lot of my work (wood siding install, roof repair, etc.).

Even if you have to use a higher-interest Home Depot type credit card, getting it installed and the units rented out would be preferable to the units sitting vacant. 

Situated on lake with a 1/2 acre.Scope of Work will consist of cosmetic improvements to include the following: painting of interior/exterior, power washing, cutting of lake grass, upgrading bathrooms, new kitchen appliances as the kitchen cabinets are in great condition, upgrading of electrical outlets, installing of new lighting fixtures, cleaning of tile flooring and etc.

I'll be adding value based on the Scope of Work which will consist of cosmetic improvements to include the following: painting of interior/exterior, power washing, cutting of lake grass, upgrading bathrooms, new kitchen appliances as the kitchen cabinets are in great condition, upgrading of electrical outlets, installing of new lighting fixtures, cleaning of tile flooring and etc.

A new roof was installed a few months ago.

We will need to fix the water heaters, replace the heating with heat pump AC/Furnace HVAC systems, replace the roof, redo the back stairs, install cameras, redo the landscaping, redo the asphalt, and install security doors.

Next, install hyper sensitive smoke detectors, wi-fi video of common areas, and hire moolighting police drug-sniffing dogs, preferably German Shepherds.  

What is the price per sheet of installing a 5/8 4ft x 8ft drywall.

The answer to that goes back to the installer.

Any recommendations for the type of flooring that is low cost but looks good, factoring in the cost of installation?