Every so often someone comes to us wanting to move an existing product, and we have to give them bad news: the store listing is in their old agency's name, the domain is on a personal account, and nobody can find the source code.
None of that was malice. It was convenience at the time, and nobody asked the question.
The five questions
1. Whose name is on the App Store listing? It should be your company's. Apple lists the developer as the seller, and that is who the customer sees. Moving a listing later means an app transfer, the other party's cooperation, and the goodwill to do it.
2. Whose account holds the code? The repository should be in your organisation, with the studio invited to it. Not the reverse. If the repo lives in their account and the relationship ends, you are negotiating for your own product.
3. Who is the registrant on the domain? Check it now. It takes thirty seconds and it is the single most common thing to be in a former contractor's name.
4. Who pays the hosting bill? If the studio pays and rebills you, your product depends on their card not expiring. Hosting should be your account, with them given access.
5. When does the intellectual property transfer? Under a typical agreement the IP passes on final payment. Make sure that is written down, and make sure it covers designs and content as well as code.
Why we set it up this way
Your code, your store listing, your hosting, in your own accounts. If you take the work in-house tomorrow, there is nothing to untangle.
It costs us the ability to hold anyone hostage. That has never felt like a loss. A client who stays because leaving is painful is not a reference, and references are how a small studio grows.
Ask these five questions of anyone you are considering. The answers tell you a great deal about how the rest of the project will go.