Not much to worry about. If the gun has NOT been totally abused, which is most likely the case if it is in possession of a reputable dealer, any problems that it may have will be taken care of by the best warranty in the industry.
However, if it has a custom ATI stock, and you send it in for service, you might get your 995 shipped back with an original stock.
Another thing to remember or to inform you of if you don't know, If you buy a used gun from a private owner or at a gun show or maybe a smaller dealer that just took it in aon trade and had not done a thing to it, Hi-Point (Bee-Miller) highly recommends that you send the weapon back to them and let them go through it and make sure it is in proper operational order. They will also make ALL updates to the weapon that it may need. This is all done at NO CHARGE TO YOU! They will even send it back to you postage paid and most times they will include a new (extra) mag to reimburse you for the postage that you had to pay to send it to them.
They truely are a great company to work with. My 995 was made in aug of 1998, they went over it, updated it to current specs and with any new parts that were needed. It was basically a new gun.
You really don't need to worry about a hi-point carbine when buying one used!
From my experience (not just with Hi-Points but with any used guns), if it looks good on the outside, then it was probably taken care of (in general). If it's beat to crap on the outside, then the working parts were probably neglected (in general). I've never actually seen a used Hi-Point for sale, but I'd have to go with the crowd and say get it checked out.