The following is my response to a question on the now defunct testing.stackexchange.com. The question was "Testing for start-up?" and my answer:
I have worked with startups for most of my career. Considering the clarification that you added to the question, it is a difficult question to answer in the abstract. A lot will depend on the team that exists today and a realistic understanding of the upcoming hiring plans.
First, consider that in a startup most people will need to wear multiple hats at different points in the early stages of the company. While the person’s primary responsibility is testing, consider what else they can do. I would lean towards a professional tester who can help with things like working with beta testers, working with interns, perform system administration tasks on the test systems, etc. It will depend on what skill set already exist within the team.
Second, consider costs – not just the salary of the person you are hiring but what items the person may expect to be in place. I made a hiring mistake at one of my first startups where the person I hired as our primary tester was so wedded to the tool set from his last company (a tool set that the company could not afford), that this person spent as much time trying to justify buying the tool as working on the product. This is probably less of an issue today with so many open source tools but keep it in mind.
Third – laying a foundation. The hire must realize that not only are they coming in to test but they are laying the foundation for how the company will approach testing for a long time. This person will help define the relationship between testing and the other groups. For this reason alone, I would lean away from part time testers or beta test volunteers. They will not be able to lay that foundation.
I would hire a professional tester. This does not exclude the development team from taking an active role in testing. The hire should encourage it.