Word to describe an informal, mutually beneficial interaction between two or more people

Context
Consider a language exchange group. In other words, people are teaching and learning foreign languages from each other. There are no monetary transactions.

I'm looking for a word that's friendly in tone to summarize this mutually beneficial concept. It should be more informal and "marketing" friendly than exchange. The best I've come up with is "mutual help," but it sounds a bit redundant to me.

Sample sentence
A community based on mutual help.

Other options
Reciprocity - too transactional
Mutual benefit - similar to mutual help and a bit sterile

The word symbiosis nicely captures the idea of cooperating for mutual benefit.

a cooperative relationship (as between two persons or groups)

You could use it in a sentence like this:

The members of a language exchange group are in symbiosis, teaching each other, and learning from each other at the same time.