Buying used when you can makes sense. You can often find pneumatic squeezers on Ebay for half what they would cost new, for example. Clecos ought to be abundant on the used market. I guess it might come down to the question of how soon do you need a particular tool. If you are ready to start building and you haven't find the used tools you need, then you will either to buy them new, or put off starting the kit until you can find what you need. Ideally, you could find a local builder who just finished an RV project and is willing to sell what he has, and who can tell you what else you might need to acquire.