Whether you should start with sole-proprietor or LLC has nothing to do with your budget but more to do with how many employees you have. If it is just you starting out you have to make it a sole-proprietor type business.
You will have the freedom to change it whenever you start hiring and you'll get a new EIN#. First thing to do on starting it up is to contact the IRS, either by internet or on the phone 1 . 800* 829 x 4933.
I just recently started up my own so I can assist you if you have any other questions, just shoot me a PM.