Form question

[Jak Dadi]

I have rented a couple of units to tenants that were brought to me by a non profit agency. Within the first month, one tenant gave us some trouble on her rent and we initiated the eviction process. We contacted the non profit agency and expressed our displeasure. Finally, the tenant did pay the rent and the non profit agency agreed to become the payee in her case and that of any other tenants they brought to us. The idea is the tenant would write them a check and they would write us a check.

My question is- does anyone have any such agreements ....i am looking for a suitable form that I could use in this case. Also, how do I verify if the non profit agency is legit. What documents do I ask them to sign? What kinda of late fees have you charged in your lease contract? Since the agreement is with a company, what due diligence steps do I follow?
My property is in the East Bay Area -Oakland). The studio rents for $600 and I ask them for one month's deposit.