Coastar made (or at least sold) a bunch of photographic items in the 1980s (and probably before and after, too). My hunch is that the Coastar enlarger you mention was made by somebody else. My impression is that they weren't exactly catering to the high-end market, so it's probably a pretty basic enlarger, but I can't be positive of that. The model name suggests it's a 35mm-only enlarger. Even though you're not currently interested in enlarging your 120 negatives, you might do better to get something that's capable of handling them. OTOH, given the price of used enlargers right now, you could always get one that's likely to be junky and use it to learn with the intention of buying something better once you know enough to have some idea of what features you'll actually want.
I notice you're in California, but the Craigslist ad specifies it's in New York. (Assuming the ad is the one that turns up on a Google search, along with this very thread!) This means you'll pay a lot for shipping -- probably $25 to $100, depending on the enlarger, how it's packed, and what carrier the seller uses. This could be more than the enlarger is worth. I wouldn't recommend spending more than about $25 for the enlarger and a similar amount for shipping, at least not given what I know and assume about the enlarger (that it's a low-end 35mm-only model). For comparison, I bought a Philips PCS130 with PCS150 color light source and controller for $50 with $24 shipping a couple of years ago. The Philips PCS150 can handle up to 6x7 MF film, supports color or VC paper using its color light source, and has handy features like a tilt head and fine-focus adjustment. I'm not trying to get you to buy a Philips necessarily; I'm just pointing out that an enlarger that's far from bottom-of-the-line can be had for under $100, so you shouldn't pay a lot for an obscure enlarger with unknown features or for a low-end enlarger.
Finally, if you decide to buy this (or any other) enlarger, you should find out what comes with it. Does it have filters for VC paper (or a color head)? What brand, model, and focal length lens(es) does it have? Does it come with any other darkroom equipment (trays, tongs, developing tanks, safelights, etc.)? You can sometimes pick up good deals on complete darkroom "systems" with all of these things for $100-$200 on eBay. If you buy them separately, the little stuff adds up in price rather quickly. You should also find out what sort of bulbs it uses. Many enlargers use common and inexpensive bulbs, but some use obscure or expensive bulbs. (My Philips is among the latter class, unfortunately; this is its major failing, IMHO.)
