To win work, contractors generally have to bid against other suppliers. To make an accurate bid, they estimate the time and materials required to complete the job. They measure the area to be painted and discuss the type of finish the customer requires. They assess the quality of the surfaces to work out how much remedial work they must carry out before painting. They might have to remove old paint or wall coverings, or repair cracks and other damage. They also calculate the cost of any essential equipment, such as scaffolding for exterior walls.
This article with comments was terrific - it was so informative. I found the advice useful. It addressed specifics like the condition of the dry wall surfaces, any additional repairs such. pin holes, chalking, smoothing of wall surfaces, absorption of paint and number of coats that may be needed. It should also include insurance coverage, and reflect the clean-up afterwards. Having a written contract with the company's letterhead is a must.