From my experience, it really comes down to your budget and how comfortable you are buying used equipment. I've looked at a few options like Boom & Bucket and IronPlanet, and they seem pretty reliable with detailed listings. Facebook Marketplace can sometimes have good local deals, but you have to be careful and inspect properly. Ritchie Bros. is great if you're open to auctions, and Mascus is useful for comparing different sellers. I'd definitely recommend checking a few platforms before deciding.