Hi I will design couple of website for designer clothing this is my first time that I'm doing serious bussines, so I will like to have so legal paper,to back me up if something bad happen like some invoice. I will like to know how to get does paper if it is any standar papers that I can get. Thanks for your time.

There are sites that may offer some kind of template, but I don't recommend this. If you are doing some legitimate business I'd suggest using a legal professional to draft and create your papers. If it's protection you want, you'll need to develop a contract. You'll need to decide what type of contract you are going to need (e.g. work-for-hire etc.) and sit with a counsil to lay out the terms in which you will do business. An invoice is usually either a bill for services or if not outlined in the contract, what payment terms will be.

Of course to keep it simple you can just define what you will be responsible for during and at completion of the job.

If you're doing serious business like you say than you should take it serious and do what guitrmn recomends...seek legal counsel....

Remember you have to spend money to make money

I agree, it would be best to get an attorney or legal advisor to help you make a contract or terms of service. Legal issues are different in every country. In the US, they differ from state to state.