Hi Vanillax, Welcome to Res =)
If you browse our forums a bit more, you will see that your drawing skills can come in handy for making TU. Other users will pay nicely for art they want drawn. As for the site, if you have ideas for clothing, please do post those ideas in the Suggestions forum! I think most of us would love to see some new styles. If you are a professional artist, send me an Rmail and I will talk to you about some other things too.
Avatars can be gained in a variety of ways, most involving some sort of interaction with the site and the fulfillment of certain conditions. There is an old guide hanging around somewhere, but it is mostly obsolete as it is 4-5 years old. It is a lot of fun though to figure out how to unlock them.
If you chose to be a rancher, it is up to you what you do! You may want to hatch and keep pets, you may want to hatch and sell them. Some users sell their hatch slots, usually around the price of 100-150K per slot. The person buying the slot sends the eggs to be hatched and the TU. Once you hatch the egg, you let the person know what was hatched, and then follow their instructions. If they say to release the pet unnamed from the hatchery, then that is what you must do, for example. If the egg fails, you do not owe the money back that was paid for the hatch. This is a mistake a lot of users make. It is not the success of the hatch you are selling, it is the slot itself.
I'm not sure what you mean by #4 though. The max amount of pets that can be hatched in one day is 3...