Give Chad Smith a call he is with Hallisky & Philipp and he specializes in Trademark & Patents and from what you are describing you will need Chad`s expertise. His direct line is 206-217-2225 and his firms website is www.hallisky.com.
Good Luck with your new business idea.
I`m not a lawyer but I`d like to offer my advice in terms of someone who has helped developed terms of service for a business portal before.
While a real lawyer such as the two who have replied will give you the real human touch, you can do a lot of prepatory work without cost. This is not meant to offend or slight any lawyers who are reading this, but it really helps to bring a draft beforehand and not be billed for hours of just simple brainstorming with the lawyer. Two simple steps of accomplishing this are to first list the legal challenges that YOU think will arise based on your experience in the business the website is engaged in. Lawyers can give definite help in this area in terms of what causes the most litigation too.
A second step is to look at the terms of service of leading retail websites as well as those of your competitors, both potentially and indirectly. You`ll notice recurring themes. "Middleman" websites must be especially careful with their legal terms in order to avoid being sued or worse, blamed in the press, for the actions of a scam artist. eBay, especially, has had to deal with this particular scourge, and their legal policies are worth a look because of this. After all, you don`t want to be sued for something you didn`t do.
My advice is to go through the terms of service of many different online companies and to examine what they are concerned with. Break it out of legalize and into plain english that you can talk about.
Then, perhaps using their language or perhaps not, whatever you prefer, build a list of items you are also worried about and the protections that you believe you need, based on what others have done.
Then, once you know exactly what you want, contact a lawyer and have them make sure you haven`t missed anything. No offense to lawyers, but they are very expensive and you don`t want them to tell you what you think, you want them to put into legalize what you`ve already decided... and to alert you to risks that you may not have thought of.
Also, don`t be afraid to accept a risk if you choose to. Lawyers are also not there to tell you what you can or can`t do, they are just there to help you understand and if you choose protect yourself from, the repurcussions of whatever it is you decide to do. You are the boss and the decisionmaker, not the other way around.
Honestly, I don`t have anything against lawyers, but many people use them in a way that makes it a very inefficient and expensive process.
[edit: I see after posting that I repeated a lot of David`s advice...]