I never do estimates by the sq. ft. but I may have a situation where I might. I recently met a contractor who deals in forclosures. Once a house forcloses he gains access to the house, changes locks, and does whatever work neccessary to sell the home. He said more often than not that is carpet cleaning and painting. We started talking and he needs a painter. He estimates his painting by the sq ft to the bank and they either accept or deny. His number is $3.50/ sq. ft. All one color (navajo white) flat, no furniture, no home owners. It seems like 9 times out of 10 if I came at $3.00/sq.ft I would still make money. Of course there are jobs where there is a ton of trim or 20 ft high ceilings then that number would not work, but I would make it up on anoter job. Does any one have a similar agreement with a contractor that works.