What requirements would I have to have to be a sys admin for a small company of 50 people?

its difficult to answer, just about every site has a different setup and support needs - but a good grounding at desktop - server & networking levels, with some project management skills should be sufficient to be able to resolve most issues, after all you'd never find someone who is truly an expert in all of them as there is just too much to know, to be able to show a friendly can do attitude and a genuine interest in what your doing, with what i've added above would impress most prospective employers