Btw: I would never buy boots second hand, even if they appear to be in good condition!
Last year I hiked the Tasmania Overland Track in the snow. I met a young lady with good quality but old, second hand boots and within 10 miles of hiking the soles started to come off, while hiking through sometimes knee-deep snow (and the girl was from Brisbane and had never seen snow in her life!). The thing is that the glue decays if the boots are not used regularly. When you buy second hand, you just don't know the history.
This girl completed the trail, but finished on boots without soles, after having spent a complete role of duct-tape on the trail to keep her boots in one piece!