I am not a lawyer, but context for this is important. Are you asking because it seems to be a risky situation? Agreed. Get an agreement drawn up.

If you're asking because things have gone sour and litigation is on the horizon, then you'll be getting an agreement sorted out all the same... just a much more expensive one, in adversarial circumstances.

If you're asking what this looks like: "Disaster waiting to happen."

If you're asking what it should look like: "There should be a partnership agreement in place that clearly states the percentage ownership of assets, and the process for sale/inheritance/forfeiture/etc."

I will say a legal "partnership" with that many people can be risky. Any idiot's individual liability can affect the other partners. Proposed 'partners' may be better served by a shareholder arrangement, or different division of assets - which would require independent and individual professional legal advice.