I will just share my experience:

We opted for an LLC and did it with Company Corporation (.com). If I remember correctly it was about $350. We then had an attorney look over the documents ($75 for initial consult) who said they were fine for a 'beginning'. We were careful to require vesting so that one of the partners couldn't 'walk away'. My only suggestion would be to have someone with LLC or legal ease experience walk with you through the application process as it isn't in plain English (at least not in my mind). You can dictate in your LLC agreement how to add equity employees and distribute more shares as needed. At some point in time, if you need to change over to a C-corp it will probably as you earn money or get funded.