I have always had the problem of hiring someone, that didn't/couldn't do the job..as well as I/we could.
My last sheet rocker,(my current house) was fired 1/2 - 3/4 of the way into the job. I purchased 10,000 screws,(2 large boxes) only to find out that he used less than 500

The 10,000 screw purchase was his request, not mine. I had a 28 x 40 man cave,(with the remainder) to do after he left.
Most rockers can hang about 2000 sq ft in a day, and start finishing in that same day. If you want yours screwed and NOT nailed, I would suggest/require an inspection before finishing. (I skipped this part...once)
99 times out of a hundred, you get what you pay for.
Check, recheck, and confirm ALL work that was done previously. If the company is new/recently formed, you might be rolling the proverbial dice.
With times being what they are, you might want to consider putting an ad in the paper for bids.
Just a few helpful hints:
1) NEVER pay until a "satisfied" inspection is performed! Regardless of payment splitting.(1/3 or 1/2 or whatever)
2) ALWAYS make a written contract! This will protect you! (and sometimes him/her..if you are a **** about the job)
3) When you tell the contractor that you are happy, make damn sure you are! because, in a year or two, you won't have a leg to stand on when the contract is brought up
Some other considerations (to do it yourself):
1) Since ceilings are the biggest pain when "hanging" sheetrock, you may consider a purchase/rental of a panel jack. I was working 12-15 hour days, 6 days a week. (I had NO time!) This only applies if you can actually hang it
2) You can always sell the jack, after you are done. The money you "might" lose will be money in the bank, after the fact.
3) After you complete the "hanging", finishers are sometimes easier AND cheaper to find, than a full service rocker.
In short, do your homework. You won't be sorry. "If" you are, its
your fault..NOT the contractors
