I think the 23" framed are relatively rare compared to smaller sizes, so while there are likely much better deals out there, you might have to wait a while to find one.
You could probably ride it as is for years as is. For a rider I would tear it down, inspect inside the bottom bracket shell, scrape, chemically treat the rust, prime, paint, maybe clear coat and wax. I've done this on a couple bikes. It takes time and a more money than you'd think for materials.
Next one, which happens to be a 23" Trek 750, is getting a utilitarian powder coat. But that project has enough sunk costs that the extra $120 seems like a rational choice...,