Ask HN: Questions for Forming a Business

<disclaimer> I'm sure this has been asked before but after a couple of hours of searching I wasn't able to find anything that really answered my question 100%. If you can point me in the right direction it would really be appreciated.</disclaimer>

So I quit my job as a software engineer at one of the world's biggest defense contractors to start my own business. I have a couple of potential clients lined up (95% sure they will be hiring me) so my income will be good for a month to a month and half but I haven't made my business legit yet and I really need to get my business paperwork done ASAP.

This venture will simply serve as a means for me to conduct business as a freelance software developer. I will not be seeking any outside funding for this particular venture and for this reason I am under the impression that a limited liability company (LLC) is probably the best structure for me because of its pass-through tax capability, limitation of liability, and overall simplicity.

I understand that I need to get a Tax ID number, and ordinarily you need to file with a state, county, and city if you are opening a business.

My question is this: Since I am not really bound by location for this venture (all I need is a laptop/Internet connection) what is the best and most cost effective way for me to do this? Do I even need to file with a particular county or city?