Oops! Just pushed the wrong button. Here's the follow-up:
First, the 2 in cai2 is as goh and flex said, the tone; and no one in China put a number to the word that way.
Second, Chinese (in China) tend to use the word "caifu" instead of just the character "cai"; but unfortunately, caifu.whatever are all gone.
Third, pinyin names are quite common in China; but unless you are a Chinese in China, you'll find selling them names fairly difficult (though not impossible) because of language and institutional barriers. And the fact is: most commonly used Chinese terms have already been registered.