How are you supposed to buy assets for your employees?

We are adopting Unity as one of our in-house tools. We have only one developer working on a particular project right now. We don’t want to buy assets on his account, because he might move projects or go on leave while someone else works on it. Someday his e-mail might need to change, or he might even quit! So, in order to keep our assets we could buy them on the manager account.

But then all our assets have to be used on the same project at the same time, even when they’re purchased for different projects. It also means a dev we hire for a project using those assets gets access to our manager account while logged in. What is an actually useful way of doing this?

I’d be interested to know what the recommended way to do this is. At the moment my boss buys any asset I want via the Asset Store in his Unity and then sends me the package to install.