QA Approach - What all should I ask for when taking over a project from another vendor

I've never been in such a scenario of documenting a strategy or an action plan to follow while taking over a project from another vendor but now i'm now.

I would like to know what all things I need to get answered from QA perspective when we are taking over a project from another vendor.

1. What all documents I should be asking them to provide
2. What I need to do if the previous vendor does not have any of the important documents prepared.
3. And any other important factors I need to consider to avoid any common risks in this scenario.