FYI, Here in Southern California the going rate for popcorn removal and application of a knockdown texture is about $1.10/sf - about $1.00 for "orange-peel" texture. That doesn't include painting. However, as a homeowner who got a couple estimates, the total cost for my 850/sf job ranged from $1300 to $2500. Those estimates included removal, priming, knockdown, and up to two finish coats. The high-end estimate added a $500 scaffold charge for my (up to) 14 foot vaulted ceiling. Hope this gives you an idea. By-the-way, I've decided to do-it-myself. Following advice from forums like this, I think it's an achievable do-it-yourself project. Worse case - I'll have the popcorn removed and need to hire someone to finish it. Anyone in the San Diego area wanna help?