Exactly how I feel too. I like to know what I'm buying is in good condition. As far as buying second hand kits I would rather have them open. I have been bit several times buying still sealed old kits. One time I bought a "still sealed" Revell's Stars and stripes Corvette kit at a swap meet, paid $20 for it, got it home and opened it , and it was a box of empty sprues and a couple of pickup truck beds. I knew the seller , and told him . He said he got it at a swap meeet also but didn't open it. Obvisouly he didn't know and didn't remember who he bought it from. Sad to know this happens in our hobby..!
One of my most sought after kits was the Revell 1/8 Jaguar, found one still sealed at a hobby shop for a decent price, got it home the windshield was broke in half
Very leary of buying still sealed second hand kits , and I try not to buy them if posssible. In my opinion "still sealed" does'nt add to the kits collectability...!