Get those 10 posts so you can buy off the classifieds. Also, lots of buying and selling in facebook groups. Just about every major hunting backpack brand has a group dedicated for buying/selling that brand of gear. You should probably talk with your adults about paypal (most common) and other payment forms before committing to buy. When buying, only buy from people that post actual pictures of their gear, if the deal seems too good to be true, it probably is. If it seems fishy, ask for a picture of the gear with a specific thing in the picture...orange beanie, peace sign, thumbs up...that way you can tell they actually have what they're selling. Backpacks are people specific sometimes when it comes to fit...just because 10 people on a forum swear xyz pack is the greates ever, it may not work for you. Buy based on the features you want, you'll never know how it actually works until you use it. The most important thing....GET MEASURED. If you have a local backpacking store or REI, have them measure your torso length, WRITE IT DOWN. That will give you a good reference when pack shopping.