I need to replace my rear wheel, and happened to get one for free that's 700x45c. I don't have any compatible tires at the moment though.

Tires that are more than 45mm wide are kind of hard to find around here, and the selection isn't good... how narrow can I go on this wide of a rim? Or do you have any recommendations for a good wider tire that's under $50? I mostly ride on paved/semi-paved town streets. Thanks!