Well, it depends on the scope of your site and what your trying to protect. Look at it this way...if you ran a site like "e-harmony" you would have several lawyers on staff to handle various legal issues that come up day to day for a site of this size.
If you have a much smaller site, your requirements are much smaller.
You will want an attorney to help you with your "terms of service"...this is the "rules of your site" and will typically attempt to waive liability on your part, say one of your customers assaults another one of your customers and the victim comes after you to sue for damages.
How much do you have in the bank? The more you have, the more you have at risk and the better the legal help you will ned.
Cost? See above...the more complex your site, the larger your site, the more a lawyer will charge to help with the waivers.
The best way to approach this is get your site "ready to launch" then contact several local attorneys with experience in tort law...you will find one to help.
Speeking of waivers...here is mine
Please let me know if you have further questions; if so I will do my best to answer them. If not please hit the accept button, its the only way I get credit for my work.
Terms and Conditions: By your continuing in this conversation with me, or by your clicking “Accept”, you are expressly agreeing to all of the following: (1) our communication is for entertainment purposes only; (2) you do not seek to establish an attorney-client relationship with me, nor do I with you; (3) you will not rely on anything I say and you will obtain appropriate legal counsel via a traditional office consultation with an attorney licensed to practice
in the jurisdiction
where your legal issue arises; (4) by communicating with me in this public forum you are irrevocably waiving any right to privacy, confidentiality and attorney-client privilege concerning the matters discussed. You further separately declare that any payment made by you is not consideration
for this contract
, nor offered for any services rendered by me on your behalf. If you do not agree with these terms and conditions, then you must advise me immediately.