A $300 boat could be a good deal, if the boat is what you want, need, & fit. Is 140 the mid or low end? Are you done growing, & is the boat made for the kind of water you want to be on? NO BOAT HAUL is good for everything, play boat hauls are a bear on flat water, & flat water boats are like a station wagon on a tight stream. Go to a "good" outfitter shop (or site), talk to them about the boat & what you want to do with it, & see if it is a good buy. Try out some types. A good outfitter may not sell you a boat now but you will be back for gear & future boats.
When you compair check, length, haul, volume, & capacity, but most of all what it is made for.