How does selling slaves work?

[Gball]

So, as to not derail the new release thread, I tried a bit more of slavery and...it is weird.

If I have someone imprisoned, I can sell him, however if that same someone is already my slave I can't always sell him. What are the requirements?

 

[ngppgn]

To add to the OP questions (given that in the manual there are no guide concerning slave trading) how should a slaver (or slave buyer) proceed? I mean, concerning declining/accepting price offers and such. A quick basic walkthorugh would be most apreciated