Hey Denise, you can always sign up with the same domain name if you’d like. As long as you have the affiliate link, you add it anywhere with one account. However, it’s a good idea to let the affiliate manager know every domain that you own, as getting approved regularly requires that they know the websites that will be sending them traffic. I hope that helps!
Affiliates decide within their affiliate programs which banners or ads they're going to place on their websites. This decision is based on their individual calculations of which company ads their website visitors are most likely to be interested in. They will also agree to affiliate programs based on which merchants have the best commission structure, although the structure is not usually considered very high-paying or profitable.