I would strongly advise any new shooter buying a used bow to take it to a pro shop and get it checked over before paying for it. Until you learn what to look for to see the tell tale signs of abuse, you could be buying someone else's problems instead of a bow.

When I buy a used bow, first thing I do is get the string/cables replaced, the axles/pivots cleaned & lubed and the cam bushings/bearings checked for wear. That all costs money, so I rarely buy a used bow unless I get a great deal on one.