Do I need to form LLC or corp to be an independent sales rep in PA?

[still breathing]

About to start representing an out-of-state company as an independent salesman in PA. I know that it makes sense to go the LLC route, but is it an absolute necessity, or can I start out without that? I'm concerned more about liability issues than tax issues.

 

[FlyingRon]

What liability issues?
What makes you think an LLC will help or the lack of one will hinder you?

 

[still breathing]

I'm concerned about frivolous lawsuits - it's Philly, after all. Also, I don't know if it's acceptable to just "hang a shingle" here in PA without registering in some fashion as a business entity. As an independent rep, I assume it's okay, but assumptions are dangerous.