On Rarible, digital artists and creators can issue and sell custom crypto assets to represent ownership in their work. Creators can create fractions of their NFT in the form a token then sell the token as an opportunity to invest fractionally into their NFT. You will make money if you buy said tokens and they appreciate in value then later selling on Rarible's marketplace for a profit.
Rarible takes 2.5% on all sales.
There is no guarantee that the fractional NFTs you invest in will increase in value after making the purchase. Rarible has a great reputation with the goal to be fully decentralized in the form of a DAO (decentralized autonomous organization) where all rights belong to the platform users. If this were the case, the platform would be in a sense driven by the community.