You can pay a lawyer to draw up this agreement if you are a large company that has a big enough budget to cover the costs, but this is not necessary as you can do it for yourself. You can of course write out your own agreement using one of the many different templates that are available for download online. Both of these documents are completely binding in a court of law, the difference is the amount of money you are going to have to spend. Each of them must be signed by both parties and in many states notarized in order for them to be legally binding.
If you are employing staff, you certainly need to implement an Employment Agreement. This agreement should be between them and your business and it needs to be clear and well defined. This is because the last thing you want to happen is for your employee to get upset and then take legal action against your company for whatever reason. The best thing you can do is make sure each of your team is engaged using an agreement that both parties have read and signed and agreed upon.