You should expect an estimate based on an actual examination of the house, as well as a plan for exactly what the painter will do. During the job, the painters should behave professionally while working as efficiently as possible to complete the job in a reasonable timeframe. Afterward, the only evidence of the paint job should be the paint itself — a professional contractor will clean up thoroughly once a job is done. 
For trim and doors, start with 1 gallon (3.8 L) of trim paint for every 600 sq feet of floor space. Purchase more at the store if/when needed. Trim is something that is difficult to calculate exactly, and it is more time-efficient to simply start with less than you need, and go buy more after you have used up the first round of paint and determined how much you will need to finish by seeing how much you have painted so far, compared to the gallons used. Denver House Painting
Supplies and Equipment – Scraping, sanding, and stripping tools and supplies; patching compound; power washer rental; primer; caulk; masking supplies; painters’ tape; ladders and scaffolding; paint pans; brushes, sprayers, and roller brushes all cost money, even if you do it yourself. Consider all of those tools and equipment sitting in your garage for the rest of your life vs. paying an experienced painter to do it all for you at a price that saves you weeks of time. Expect to pay $5–$6 per 100 sq. ft. for supplies and materials. Home Painters Denver CO
Power washing – $0.42–$1.40/sq. ft.. You might think you can save some money by power washing the exterior yourself, but homeowners can get a bit trigger-happy with a power washer in their hands. The pressure from the washer can take them unawares, breaking windows, leaking water into window frames and siding joints, and gouging wood. It’s probably wiser to use a hose and scrubbing brush. Rinse off any cleaning solutions thoroughly. Denver House Painting
Determine the coverage area for each color and estimate the number of gallons you'll need for each. For odd walls with angled ceilings, make your best guess. If you're not comfortable doing this, measure the wall at its highest height and multiply that by its width. Now subtract the lowest height from the highest height, multiply that number by the width, cut that answer in half, and finally subtract that new number from the original height by width. That should give you the wall area. House Painting Denver Colorado