You can try Roofing.QualitySmith.com i found this with a quick search they offer an on line bidding system. you should ask the roofers if there insured, there experience in roofing, for some referrals also make sure to get several bids. a job like a roof has a lot of labor cost in it so bids will vary. id also get bids on the job with a tear off and an overlay. if your replacing the air cooler then the installer of the new unit should disconnect and remove it properly. roofers might brutally remove it and destroy mounts,connections or duct work and make more repairs for you. plus they may throw it off the roof Ive seen it done.

Things I found: reglazing a tub...only splashed some paint on it; replace light fixtures...actually found some second hand light covers which were mismatched, in the same room; painting...they didn't cut in or mask and painted over light and outlet covers; replace and install window blinds; they used the existing mountings to install blinds even when the original mountings were done wrong (they charged $45 per set and used $10 Walmart blinds); patch, sand, and paint drywall...they patched and painted, but didn't sand.

The brief research I've done has shown mount washington and east liberty look solid for rentals.

I’ll just keep it short and sweet and chat about the huge amount of love Motor City has received in just the past few months from the Big 3.

Investment Info:Large multi-family (5+ units) buy & hold investment in Mount Washington.

I have 2 duplexes in Hamilton Township and a couple of properties in Mount Laurel.

As for holes in the wall anything you mount on those walls or ceiling IS a whole in the wall.

Drive the surrounding blocks and note if (a lot) of the properties have window units.If so, it might be norm for the area.Also talk to 2 or 3 top selling Realtors (in that area) and get their take on the value add of central A/C and how common it is in that area.Not to say you can't be the only one offering a central Air unit in that area, just go in with enough information to make a reasonable decision.Window A/C comes in many different AMPS, if renter A brings too big of an amp draw for the circuit it must plug into he will blow fuses or breakers all the time.If you own the window units, you can have a dedicated circuit run that matches the AMP load of the A/C, in which case using a sleeve unit makes sense (they are a little different than window A/C), because it does not block the view, and you can mount it up high and let the cold air fall, or mount it down low out of the way.The downside to window and sleeve units is some renters will steal them and then claim to not have stolen them, so you have to ding their security deposit for it.And like @Bruce Woodruff said, there is the minisplit option.

i find all units you can rent or purchase to be worthless other than the large commercial grade/truck mount units.  

Every apartment failed for small issues (gfis, fire extinguishers present but not mounted, smoke detectors are now required to be photoelectric- not ionized, outside railings need to be raised).