Buying second hand is a bad bad bad idea,
all kinds of crap goes on here with tires and if you're not familiar with them I can guarantee that you will get screwed over. I have seen people carving out grooves by hand, polishing tires up with shoe polish and oil, then u have re-treads and all sorts of other stuff to make the tire look good, I would advise that you always buy new, even if it's General, although better brands are not all that much more expensive, perhaps consider something like Dunlops from indonesia or something similar to suit budgetary constraints.No matter what the dealer says, a used tire is removed due to some problem or the other in Pakistan, no one would replace a good set of tires for no reason in an 800cc vehicle. That only happens in higher end vehicles or SUVs.
What ever you go for, always go for a new tire and try to stay with a tried and tested name, even if it means going for General, you don't want to risk having a tire blow out at 50-60km / hr or above it could be fatal and it's not worth it to save a few thousand rupees.
As mentioned by Storm, check the manufacturing date whether u end up buying old or new.