How effective of a marketing strategy is it to recruit guinea pig companies to try out my service?

I have a solid idea for a company that is in its very beginning stages. However, the startup cost is very expensive and to avoid unwanted debt, I will need to recruit a few guinea pig companies to host my service for employees so I can see if this will even work out. But obviously I will need some inventory in order to get started. As much as I believe in what I am marketing, I strongly dislike cold calling and/or being a walk-in. Is this the best method of marketing (besides advertising, which is not an option at the moment).