The extent... hm.

I think my answer is: The extent as what I could do for a really good friend.

Your best friend would care for you naturally, and you for him/her. The extent, in this case when it comes to business is really whatever you'd be able to do for him - as long as it delivers value to everyone involved. Of course sometimes...

It depends on the person him/herself.

When you can trust each other, have a relationship, the extend can be far further.

Sincerely,
Chong Xin Yun Seth
http://www.bookedcopywriter.com