The price and requirements will vary according to how large the school is and how well know. A Doctorate from an unknown online school, may not have much credibility.
I would look up "higher eduction" or the names of some schools. Get several brochures and lots of information before you make your decision. Also, call some of the major universities and see if they can recommend some. There are many out there that will let you basically "Buy A Degree" but you will not have a quality education and they will not be cheap either.
It is not normally much cheaper to take classes online than it is in the classroom. It is just a lot of off the wall colleges offer an easy way to get a degree. As far as doctorate degree, I am sure it would be much more difficult and very expensive.
Maybe you could consider taking some of the basics online and the others at night (if you cannot go during the day) at your local college.You can earn credits a both schools. Just make sure they will transfer to the school you want to earn your degree from.