Am i on the correct way?

Hi, i’m trying to create something like ipfs cloud storage. For using it, you need to pay coin, and for earn coins, you need to store data from other nodes.

As i undestood, there is no api for detection from what node i downloading. So i want to pay for finding your node in findprovs, yeah i know it’s not good idea, but for my app it’s enough.

So question is, is findprovs storing all hash and nodes which abble now? And how long the hashesh will store, after node goes offline?