I disagree with those who say "
it's a terrible option". Unless you're a power user or want to 'tinker under the hood', don't knock that little Mini. Coming from Windows (unless you had an all-in-one), you probably have a monitor, kb and mouse, so that $499 will give you a brand-new, nice little entry-level Mac that runs Yosemite, and comes with full warranty.
Other than that, for a budget of $500 you'd have to take your chances with an older used Mac, or get that latest version entry-level Mini from the
refurb store for $419. A good deal really, considering Apple's refurb QC, return privileges and full warranty. Also from the refurb store, for a mere $589 you can get a considerably better Mini with a 2.6GHz d.c. i5, 8GB of memory, a 1TB HDD and Iris graphics.
If you decide to go the route of an older used Mac, I would advise against going with anything older than 2009-2010; running Yosemite might be a problem, but mainly for ease of parts availability. Hope you find what you're looking for!