It depends what state you are in. I am in Colorado and the Secretary of State has a self serve $50 and 10 min worth of an application and you are done. Of course, only you and an accountant can determine if you want LLC or S Corp or whatever. Check with your state to see if they have this resource. I know that LegalZoom, although thorough, can get spendy for something you in many cases CAN do for yourself.
I had my prepaid attorney spend about 45 seconds telling me exactly what to do, then I did it myself. I of course had to get the LLC licensed, too. This was in the socialist state of California. I don't know where you are.
As BADTROUT mentioned, you need to figure out what is best for you. I did a lot of research, and an LLC for my situation, goals, needs,etc. made sense. For someone I know in a similar but slightly different situation, a partnership made more sense.