I'd start with local agencies that provide support for people experiencing homelessness and addiction. I'd also look to work with anyone who might be seen as a "community leader". If you're looking to open a wet house then you'll need great staff, but you'll also need good working relationships with other agencies. If you can't get the local government on your side, then you're doomed from the outset. You need people who are connected and know how to work the system.
