Yours is flat roof. There can be different materials.

If I do it I probably budget at 10k: 2.5k material, 1.5k disposal, 3k labor, and 3k gross profit, not including insurance cost spread through jobs. Remember insurance for roofing is more than 2k a year each person, so unless a company does not have a lot of business, they can not survive. 

But your location is more regulated by government, so I can't tell...