Arbitrage involves identifying opportunities to exploit differences in pricing across coins, protocols, platforms or whatever and making automated trades to take advantage of those differences. It is the ultimate money making machine, literally creating money out of thin air. This will require keen insights into how to identify arbitrage opportunities as well as sophisticated development skills to ensure there are no unintended consequences.
There are various types of nodes that can be operated for profit. The old school form of node was mining, but those days are past. A key type of node currently is Chainlink Validator Nodes.
Education of the masses is one of the key components of the wide scale adoption of blockchain. Dapp University is a prime example. We could do much better.