mcotten - 6:58 pm on Mar 24, 2013 (gmt 0)
You can share your Google Analytics account to another Google account holder with access to reports only. As the administrative account holder you can remove them at any time.
That being said, I would not give that access to a seo consultant that solicited you because most of those are not reputable.
If you contacted an seo company because you did a search and they had the ranking and/or because of a reputable client list then I wouldn't hesitate to provide them access to your Google Analytics as they will need to run their own reports to evaluate your website.