We are designing a Sharepoint site that will allow two different companies with different permissions to colllaborate.

We have a requirement to create two document libraries. The first library will be accessible by both companies. The second library will be accessible by the host company only. Documents will be created in the host company library, and then eventually moved to the other document library that is accessible by both companies.

Is Sharepoint "out of the box" capable of doing this? How would I do this?

The only thing I have found that is even close to what we need is the Send To Other Location function that is available to any file. The problem with this function is you copy, not move documents.