When the homeowner is at the point of hiring a painter, they generally will have colors selected or at the very least a color in mind. I always ask for the colors before I bid a job. Dark colors, high sheen colors and specialty finishes require more labor, this drives price. If its not a color change or I'm going over a similar color I give the pricing option of one or two coats. The best advise I can give based on 25 years in the business is to put it all in writing,colors, brands of paint preferred, when the work can be done, who moves furniture and how payment will be handled. I never get up front money. BTW you most definitely get what you pay for with paint. Higher quality products results in and better looking job. Don't be a cheapskate when it comes to paint or the painting contractor.
A good contractor doesn’t just do quality work, of course. Workers should be courteous, pleasant, and capable of clear communication. Ideally, the people altering your home’s look will be enthusiastic about the task rather than jaded and burnt out. Find out from your references what kind of attitude the company’s workers displayed, and whether they behaved professionally. Also ask whether the crew stayed on schedule, and whether they arrived early each day, did their work, and got out of there.