D. - You are potentially going to get your butt kicked in the forum for
asking. There is no really good way to determine. If you trust this
guy, has done good work for you in the past, shows up on time and is
sober on the job site then pay his rate. Less headaches and money well
spent.

Sq. Ft. price? I would say $60 to $125 per sq ft. More or less. If his
price is more than that then did you ask for it to be done in a week?
Did you give him a lot of headaches on your last project? Is he so busy
he doesn't want the work? Did you specify super high end finishes and
fixtures? If his price is less than $60/sq ft then I might be concerned
he missed something.