www.bubbasikes.com
www.mooseburger.com
www.clownantics.com
www.luckysclownsupplies.com
www.indianaclowns.com
These will help you get an idea of what the stuff costs. I am lucky, we have a great costume shop that we frequent. Her prices are inline with what we would pay online for the same thing. She was very helpful when Sassy was looking for a new wig, and helped me find a suitable replacement for the Steins Carmine red that I have used for years. To me, there's a lot to be said for old fashioned service.
There are several good brands out there. Ben Nye, Mehron,Proknows, amd Jim Howle. I do not recommend that you use halloween makeup. The stuff doesn't set properly and isn't really designed to stand up to the wear and tear of clowning. This was something I found out the hard way! I can sweat the stuff right off, and Powder doesn't set it properly.
As far as Local clowns who aren't willing to help you learn. I haven't heard of anyone having a problem in that area. I agree with jamz, look for a Coai or World clown association alley in your area. They are there to help you learn the art. I have heard of those problems, but have not experienced this myself.
You might also search Red Cross. I am a Red Cross Clown, as are Sassy (That would be Mrs. Scruffy) and Doc and Jasper. Whom I have the great priviledge of working with. In fact I hooked up with red cross because of meeting Doc at an event that I decided to work on my own. They actually broke the rules and let me clown with them. He and Buckshot needed the help too. They were swamped! But it's a ghrat group. I wouldn't want to be anywhere else.
Also a little personal history on me. I became a clown in 1982 at the ripe old age of fourteen through 4-H. I stopped clowning about three years later. In the fall of 2003, I decided it was time to start clowning again. I dusted off the props, found my now 20 year old makeup, and had to recreate my costume ( Pretty close to the original). I also re read all the books on clowning that I had learned from and evern found two newer books that are excellent. I feel that the twenty years I took off really didn't effect my ability to be funny. I feel that It was helpful. In that time I had discovered from personal experience what worked (As far as humor) and what didn't. I also had become a parent. So I had first hand experience in what kids found funny. I guess in my mind, I never stopped clowning. I knew that someday I would take it up again. You are never to old to become a clown.or in my case too old to become a clown again.
As far as others protecting their territory, I believe that competition is a good thing. If nothing else, as a parent, it lets you alternate party entertainment so that the kids get to see a variety. A good clown should not be worried about a little competition for another clown.
Good luck!
Scruffy