Vault questions

[Guu]

So yeah, a friend wants a vault to put their artefact in. I have a base to put it in.

1. Can they pay fully for the vault even if it's not their base? Like if I give them permissions as such to do so.?

2. If not, could they pay half for the vault while I pay the rest?

3. If 1 or 2 is a yes, how do permissions work? Do we both have access to the vault? In the case of 1, does she need to give permission to me to use the vault in my own base?