On the low end they are roughly 50% more expensive than your typical shingle roof.

Are the roofing shingles in multiple layers, dry, cracked, and peeling up?

Well the original roofer sent out a helper who just kept plugging the hole (I think he came out 3 times) and it kept on leaking because it was a low pitch roof that needed a membrane and not shingles.

We own and self manage about 800 single family properties (90% Single Family Homes and 10% multi family), build new construction for rent (no custom builds or for other people; however one of the LLC's holds a general contractors license so it bills back all expenses of the build to the entity building the house and most payroll is ran through it as well), we have a warehouse with over 10K skews for material we buy in bulk (shingles, flooring, hot water heaters all the way down to individual plumbing connectors and paint brushes) and we buy about 200 properties a year with the vast majority of them needing extensive rehabs.

(that kind of points to an interest in this type of work).What do you want to learn, to paint, to install kitchen flooring, kitchen cabinets, to shingle a roof, to replace windows, to residing a house, to install a new bathroom with attractive tile and a big mirror, build a deck, patch plaster, etc...How are you with tree trimming, or digging holes to put bushes in.... 

On one property, they took some pictures of the property and the "inspector" (guy that takes pictures of the properties) said the roof had shingle issues and needed repair or replacement.

@Matt T.If I were doing it, I would go with a red/brown brick color, almost a khaki on the siding with a white trim around the windows & eves with dark shingles..

For example, call a roofer and ask what their average cost per Square of Architectural Asphalt Shingle Roofing would be on a 1,500 sf house, with a 6/12 pitch.

New roof is capital improvements a few new shingles is a repair.  

Our company was under contract and after due diligence they removed all the shingles off the roof!!