Do LLCs differ from state to state? And are there different kinds?  Also, can anyone recommend a really good site where I can purchase these things online?

Yes Swiney You need a LLC to protect yourself and your investments.LLC can save you from some taxes and makes all your selling advertisement process legal.Because LLC is seen as a separate person (entity) by the law and you as the owner would own a certain percentage (usually 100%) and in the case of something happening with your advertisers (they are not satisfied with your promotions, they had something bad happen to them because of the banners on your websites etc) they wont be able to make you personally liable to pay them a sum of money which they may ask (so your private accounts will be safe) they would have to take this steps with your LLC.There are many other reason, but this seems to me one of the most motivating ones.By the way laws of LLC might differ for every state. Also if you want to read more about LLC and the advantages but also the disadvantages it brings go here to wikipedia P.S. if you think the reply I wrote is abusive in any way please contact me via PM or via email if you are a moderator/admin! ---This post was edited to remove a commercial link. Read our discussion policies for more Community best practices.

Agreed with Bizresearcher people tend to go the LLC to avoid liability from lawsuit. Since as a sole propritor all your personal belonging can be tied up if someone sue you.

If you will make money from your web site, you will need to register a business name and entity type, but it doesn't have to be an LLC. If there is no liability associated with the site, then you might start as a sole proprietorship. In most states, to be considered a sole proprietor you need to only register the business name, no additional paper work.