Did you consider lead paint, old plumbing, old water pipes, how is this building heated/cooled, and how old is the heating cooling?

In northern climates the tile is cold On your feet unless heated so becomes less desirable.

Senior voucher holders typically have 1 and two bedroom voucher sizes and do like it where utilities are included as much as possible.  1 bedroom vouchers where you pay heat can be a homerun scenario if you have smaller units.  

Limit them to a designated area.If they are heating the coop with a heat lamp in the winter time, require rental insurance by the tenant if you don't already.

Solid black shingles will wear faster in the sun as they absorb the heat more quickly.

Install heat pumps for each unit?

I have tried heat - blow dryer works great - but would take many years to complete ;)Does anyone have any methods that will remove the mastic without using oil?  

One has heat and is insulated.

(Check Trulia Heat Map, Spotcrime.com, crimereports.com)2.

Central heat?