dog walking newbie

I'm not planning on being a sitter, but I do want to do dog walking. I just need to pay the registration/background fee now but had some questions prior to going for it. Do you need to supply your own doggy bags for walking the dogs? Or do the owners often supply those themselves? Also, are there ever many people requesting walks in the fall and winter? It's getting colder where I live, and I'm worried I won't get many clients if at all.