Regarding cost - Keep in mind some older homes may cost more due to the EPA RRP lead paint rule that was placed in effect. I'm not saying price will be doubled, but it will add some more labor and material cost. After all, the EPA is fining non compliant contractors nearly $38,000 per non compliant violation. I see many posts about illegal contractors. We do pay insurances, we have business costs, I price jobs to where I am comfortable with paying labor, expenses for my business, and not making $250k per year as some do. I have gone into homes where someone thought they were getting a great deal and ended up calling me to fix mistakes or sloppy jobs. Paint will vary in cost, yes.
Don't hesitate to ask all the questions you need to feel comfortable hiring a professional. You can also ask 3-4 professionals to make sure you have the right quote in mind. You must make sure they have a warranty or some kind of paperwork stipulating the quality of their jobs. Insurance is also a #1 priority to consider, as damage can happen in the process of painting.
"Rafael was very professional, detail-oriented, pleasant to communicate with (responds promptly, returns calls, confirms appointments) and always showed up on time. He painted my daughter's room beautifully and for a reasonable price (offered pricing with and without paint). His work was precise and without mess. I will definitely hire him again for more painting projects."