Do i need to start a corporation to get a business license?

I started my own business on the side and just got my first client. He just signed up for my marketing service at $2,000/mo. and he is paying by check. I hardly had any money to start the company and therefore never filed an llc or got a business license. I put my money in designing the website, getting a virtual office, and leads. Now that I have my first check made out to the company how can I cash it??? I think I can do it with a business license from the local courthouse, correct me if I am wrong. or do I need to start a llc to even get the license. I really just need someone to tell me what to do, If I have to file the corp to cash the check I will, I am just looking to cut costs until I have tht check deposited so I can pay for the llc. Thank you