That said... the lower price that people get from me does not include the assurances that accompany an insured professional. These people take a risk everytime they let me into their home, because if I trip down the stairs and break my back, it is they homeowners insurance that is on the line. If I stupidly step onto a granite countertop overhange and snap it, I have not liability insurance to sue.
You might pay an additional $1 to $5 per square foot for optional repairs and updates. Consider having your molding, trim and baseboards checked while you have a professional in your home. This might be a good time to upgrade or repair any cracks, warps or other issues. Pros can usually touch up or replace these items for an affordable rate, and they may even package such fixups with your project.
Take for example, I charge 1.75 sq foot for 10x10 room with 8 foot ceilings. By my calculations this would cost $175 with floor space sq foot, but with you method, it would cost $576.00 That is outrageous. Of course I didn't subtract the windows and doors, which is another thing that makes no sense. Cutting in around those windows takes more time, then just rolling a wall.
this was the estimate i received and well - hard to describe area - double hight ceiling entry foyer plus stairway up to hallway. painted hallway as well with 2 coats plus did a coat of white over all trim/molding/door frames - 6 of them - and repaired some minor molding cracks. we are supplying the paint. at first i thought this was high but then, well, it was better than doing it myself and the painter was highly recommended and he's very nice.
Whether doing it yourself or hiring someone, buy the best quality paint you can afford; it lasts longer and in some situations requires only one coat of paint instead of two. Painting a room usually involves prep work, primer and latex or alkyd paints with a range of finishes. HGTV.com gives a quick overview  as well as a list of painting dos and don'ts .
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