I'm needing to replace the current two layers of shingle roofing that I have installed on my Duplex.

It covers tenants injuries (a loose shingle fell off the roof once due high winds and hit a tenants car but COULD HAVE hit a tenant) We would be covered under policy. 

Buy a pick up truck , or trailer , you could go all out and get a dump trailer .I usually keep a 5 x 8 single axle trailer on my rehabs for trash so I dont tie up the truck bed ( no dump fees for single axle around here) I have a dump slide in for the truck for shingles , dirt , anything hard to unload .

Another guy was hired to pick up shingles and averaged about 2 per minute.  

Hi Account Closed , This type of software is known as CMMS (computerized maintenance management systems) in the property management biz.

Most shingles these days are multicolored, I'd probably go for that style in medium/light grayish hues.

Look for major issues like curling roof shingles, get a feel for the block, etc.

The repair work is not easy on a 100 year old property with lots of 'deferred maintenance' or shoddy prior work - look for electrical problems - faulty outlets, lights improperly installed, knob and tube wiring spliced into romex wiring spliced into BX cable; plumbing problems - lead pipes, galvanized pipes, PVC pipes, leaks, water damage evident in the plaster ceilings and in the flooring; old roofs with multiple patches and multiples layers of shingles with steep pitches; bad siding or asbestos siding that is old and needs to be replaced; absence of storm windows; old windows that don't open/close smoothly and may break; lack of insulation causing high heating bills; cracks in the foundation - cracks in the old plaster - costly to fix; do not be misled by the low entry price - I would focus more on the drive out price - do you want a rehabbed property and if so, what is that going to cost you [could be $30-$50k] or do you want to be a 'slum lord,' i.e., do minimal repairs and have a crappy property that leaks and will never be clean and chase tenants for rent. 

On another thought, what are the ways I can effectively and efficiently deal with asbestos siding, roofing shingles, and the like? 

However after dealing with roofers and the vendor, I know know that the shingles we use cost $75 a square and the roofers I use install them for $70 a square.