Best Practices for Clay Integrations with Clients

Question: It looks like I may win a few clients for whom I’ll want to do Clay integrations for. What’s the best way to do this in terms of:

1.
Should each client get its Clay licence and I get access OR is there an “Agency” model where I own the accounts and pay Clay directly?
2.
If it’s the latter, are there any advantages in terms of cost/credits?
3.
If it’s the latter, and at some point the client wants to take it over, how can I hand their Clay workbooks/data back to them?

Thanks