We had the heating system quoted and the contractor suggested we change to forced air and put a furnace in the basement and in the attic.

Sure as long as the scenario makes sense Cody just dont be living in a bel air mansion and then try to purchase an owner occupied 4 plex in a rough part of town because the underwriter will have to pull out their decline stamp.

I'm an Air Force guy myself and started investing back in April.

Don't change your air filter frequently enough and you reduce the life of the unit, not to mention its efficiency. 15 min here or there could make the difference between hundreds or thousands down the road.

The supply lines are at floor level under the cabinet & I've used Jedd's idea of loosely skirting with good air flow in front of the back of the box with pond liner. 

I'm an Air Force guy myself and just got started investing about 8 months ago.

In the Air Force all you need is 2 years of service or E-4.

Welcome @David Hartmann,I am an Air Force veteran and a new investor to BP myself (my wife is also an Air Force veteran).

Three story apartment complex, Built: 1970Number of Units: 29Gross SF: 23,184 SFAverage SF: 653 SFNet Leasable SF: 18,989 SFRoof: Slight pitch asphalt shingleHVAC: Forced hot air, gas furnace/central ACNeighborhood Class B Properties Class B-Rental Unit Income $212,911Vacancy $17,609Effective Gross Income $195,302Laundry $2,199Garage $960Other Income $4,192RUBS Bill Back $2,379 Total Other Income $9,730Gross Operating Income $205,031OPERATING EXPENSESAdvertising/Concessions $6,115Cable $8,344Management $10,252 (should be $21,291 for 10%)Office Supplies $239Employee Benefits $0 Legal/Credit Reports $1,078Landscaping/Snow Removal $3,730Cleaning/Maintenance $1,956Repairs/Supplies/Maintenance $19,073 (should be $21,291 for 10%)RUBS Utilities (Water,Trash, Pest) $18,451House Gas/Electric $1,944Real Estate Taxes $21,276 (should be $36,000)Insurance $4,400 (should be $8,400)TOTAL EXPENSES $92,192 (should be $125,109)NOI $205,031 - $125,109 = $79,922$79,922/0.08 (cap rate) = $999025I did change some number for management, insurance, repair and maintenance.

It doesn't matter how well ventilated your attic is - warm moist air from a bathroom hits cold air in the attic = condensation.