You should be able to get a very nice, servicable .22 for $100, especially if you're checking the pawnbrokers. Action type is pretty much up to your personal taste and how you like to plink. As a general rule, BAs tend to average a bit more accurate (with ammo they like) although a quality pump or lever can give 'em a run for their money. Not to say that semiautos don't shoot, many will surprise you with how well you can hit with them. Just that manual actions are better suited to using the standard velocity/Match loadings which usually deliver the most consistantly tiny groups.
Mossberg is a fine brand. Whatever you choose, be super-critical in your examination on any used RF. because they're so cheap to shoot many, if not most, will have seen pretty extensive use. Look especially hard at the muzzle's crown, the bore and chamber, and the extractor. Any obvious damage or extensive visible wear in these areas should get a pass , no matter how cheap. Signs of honest wear are one thing, but any signs of possible abuse or neglect should eliminate a rifle from your consideration.
While many like a box magazine, I still prefer a tube on most rimfire repeaters. They hold more ammo, they're less prone to loss or incidental damage, and they don't protrude right at the natural balance point (as most single-column boxes do) making hand carrying and taking a really solid standing firing position tougher than need be.
Pay attention to how things "feel" as you handle and manipulate the action on a prospective piece. It can tell you a lot about it's general condition, if you're tuned-in to listen.
Prices will vary wildly depending on a number of factors. Demand/supply for a brand or action type in your particular neck-of-the-woods, the relative rarity of or collector interest in a particular model, and -always- the condition of the individual piece make sweeping generalizations pretty much a matter of opinion. Value is relative, and always personal and highly subjective. Without a specific make or model mentioned, it's almost impossible to say with any accuracy. You've set your dollar limit, all I can tell you is to look critically for the nicest example that fits your fancy and budget.
