I have an internet based T-shirt business and it’s been kind of slow. I’ve been approached by a local company that specializes in SEO and was wondering if anyone has any experience and results dealing with one of these types of businesses? The cost is $129/mo.

I would not go for a company to do any SEO to business site if i were you. Hiring an SEO company will lead you to get into trouble because

1. They link farm and spam links
2. When links are produced very quickly of course for sometime you will be in the 1st 10 pages but once link spam has been identified you are in most case would be sandboxed. i.e is deindexed .

What i recommend you is my friend implement your own SEO campaign for your best suit. You can go through these 2 links to monetize the best out of SEO and traffic building