My recent experiences with 500px were completeiy disappointing.
In my opinion, the level of their customer service is much less than acceptable as good business practice. I am a professional photographer and recently had my paid subscription account deleted soon after payment. Of course, no refund was returned to me and my payment was simply lost. It makes me wonder how much revenue is generated in this way.
In addition, when I contacted their "customer service" unsubstantiated claims were made regarding my copyrighted, photographic, intellectual property. Two 500px employees claimed in writing, via email, that I posted other peoples photographs. This was neither communicated to me or substaintiated in any way. As a professional, I most certainly would never do this and find this claim appalling.
Again, in my humble opinion, be careful here. There are other excellent sites available that offer an overall far superior experience. The only basic value here is to subscribe to the free option. Good luck! And Good Photography!