Provide payment processing to my community I want to create a simple app to allow people accept Bitcoin in my community with low fees. I was thinking to build a full node on my server and made all of the transaction pass through it, do you think is a good idea or there is a better one?
Yes, it is a very good idea to run a node for a community, where people trust each other, but not the entire world.

Your node provides the trust about a payment going/coming through. The key is to limit the trust to this and not more. 

Let every person hold their own keys and wallet software to spend their received money. Let them only consult you about the state of the blockchain. You can do this by exposing your node as an explorer or by allowing people in community to connect to you privately(api, rpc calls etc)

If you are concerned about hosting due to legal/logistics business, provide people a method to access &amp; compare as many publicly exposed explorers as possible, to consult for txs, but people need to hold their keys.

(A meta discussion is that over time you might even want to run a mining operation for a truly sovereign community.)