Some contractors work on time and material others on a firm contract. I would never hire the former and am leary of the latter. A contractor may low-ball a bid to get the job planning to make a killing on change orders. If you say good morning to them, they charge you extra for that. If the contract is not very, very specific and extensively fleshed out or if they display their change order schedule prominently on top, show them the door.
You can save a bundle by doing the labor yourself. The biggest DIY expense is paint. Other expenses include buying or renting supplies and equipment, like caulk, primer, brushes, rollers, tarps and ladders or scaffolding. Freeman advises applying paint with brushes, not a sprayer. “If you overspray all the window frames and overspray your shingles and your sidewalks and the brick on the front of the house, you do damage that is not easily fixed,” he says.
• One room or the whole house? Applying one coat in one room is a reasonable DIY Saturday project (especially if you have help and beer). Multiply the time spent moving furniture, prepping walls and sanding old trim by the number of rooms in the house, and you might want to hire real help. It's the same outside. You can probably tackle one shady garage wall that needs a little scraping and sanding plus a coat of paint, but covering all surfaces of the house is usually best left to a pro.
When I had my interior painting done, after clearing out all of the furniture, myself, I also removed all of the wall plates in all the rooms to be painted. They were a beige color and probably yellowed. The wall was originally an off white and I had it painted a light-mid grey, so those wall plates would look terrible. After pricing replacement plates, switches and outlets (Would have been way too expensive to replace all of them), I decided to just paint all of the wall plates, switches and outlets (Used just a black gloss spray paint). I sprayed the plates outside and used a small brush on the switches and outlets. It worked out just fine and the blacks plates, etc compliment the wall color. It has been 7 years and the plates, switches, outlets are holding up well.
Home Painter Company