Thanks, all, for your time & efforts adding to the article & comments, especially Dave urging requesting both General Liability AND Worker Compensation insurance certificates to protect from real & fraudulent liability--from my experience especially in California, where insurance fraud is a popular income thief, even causing car collisions to collect.
Some proposals simply say to paint the walls and ceiling and never specify the number of coats to be applied. If the colors are similar enough, it's possible to get away with one coat of paint and not discount your pricing. No matter how hard you try, tiny, pin-sized air holes will pop exposing the original walls. This may not bother you if you can't notice it, but principally speaking you should have paid your painter less for the work.
To get basic measurements, measure the length and width of each wall you want to paint in inches. Multiply the length and height together, and divide by 144. This will give you the square footage for each wall. A gallon of paint typically covers around 400 square feet. In some cases, you may need a primer 2 first, then a single coat of paint, meaning that you may need one gallon of primer and one gallon of paint to cover 400 square feet. However, if the wall requires multiple coats, this will increase the total amount of square footage required, and therefore the amount of paint.
This painter Scot never came and finished the job. Texted me at 6:30 in the morning saying that he isn't able to do the job I gave him. I would not recommend this painter to anyone. I will make sure everyone I know won't use this guy. He is the worse business owner I have ever met. I don't know how he is in business. Be very careful of this guy Scot. Don't trust him and don't pay him for anything for any work.

Specify whether the contractor or you will supply the paint. Check Consumer Reports' paint ratings: In its tests, some relatively inexpensive paints performed better than more expensive paints and cost $10 to $20 less per gallon. But keep in mind that most paints will resist cracking, peeling, mold and mildew. Who does the painting — and how well they do it — is more important than what's in the bucket.

Ideally, you want as much paint on the brush as you can control without making drips or blobs. To do this, Doherty dips his brush about 1 1/2 inches into the paint, then taps (not wipes) each side of the brush against the side of the can. Tapping knocks off the drips and forces the paint into the bristles. "The brush releases the paint just like a fountain pen," he says. Weeks agrees, saying, "Just be sure to keep your brush moving, or it'll start to drip." For more delicate work, such as when you're painting trim or window sash, you'll want less paint on the brush. Doherty again dips and taps his brush, but this time he also scrapes the sides against his can. "The outside bristles are drier and easier to manage," he says, "but there's still plenty of paint on the brush."
Pros prefer 5-gallon buckets with a roller grid to roller pans. They hold more paint than pans and, says Doherty, "It's tougher to tip over a bucket." A bucket also lets you box, or mix, two or three cans of paint to avoid color discrepancies. To use a bucket and grid, dip the roller a quarter of the way into the paint and run it over the ramp to work the paint into the nap.

Paint Contractor Company