I haven't seen any mosins in the price range recently around me in a while... I paid $129 for my 91/30, but I've seen them $99-$150 in shops and at shows. $89 is a good price to pay for one... I think it would be hard to find cheaper than that, sometimes see them cheaper than that online, but you'd have transfer fees, shipping etc... and you wouldnt really get to eyeball it at all first.
Things to look for I guess would be see if sn#s match on the bolt and the receiver, check the condition of the bore. Pitting and rust is all bad... check the stock for cracks, and I guess it wouldnt hurt to ask the guy at the shop if he had different ones to look over if your not sure about that particular rifle... the store where I purchased mine had a pile. There were numerous armories that produced these, and over a long period of time... different models, carbine legnth ones etc. Know what your buying, and enjoy it! there are a lot of good online mosin-nagant resources out there... do some reading, but don't dawdle too much lol.
http://www.7.62x54r.net/
I'm almost done sporterizing my mosin (hiss hiss), I've sunk ~double the purchase cost on it easy in a fancy trigger, scope mount, scope, etc. I'm not sure I'd recommend doing this, as I could have bought a good "newer" dear rifle for what I've put into the mosin so far. I'm hoping it will pay off when I start shooting surplus ammo though... I'll post post when my Richard's Microfit stock arrives and everything takes shape, pretty excited about that.