Concrete walls must always be prepared before painting, but in some cases previous finishes will also have to be removed so that paint doesn't peel or chip off. Additionally, special sealants, primers and paints may be applied to ensure concrete's endurance in face of the specific elements. Depending on the wall's condition and exposure to the sun, painting professionals will usually estimate between $500 (~250 sq. ft.) and $2,000 (~1,000 sq. ft.), depending on wall area to cover.
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.
Can't speak highly enough of the service we received from James and his team. I did my due diligence and met with 3 painters. If I'd have met with James first, I might have skipped the other meetings. He talked me out of some extra work that wouldn't have come out the way i'd envisioned and showed me a packet full of successful projects, happy clients that dated back to the 1970s.