Slaves can't bid on surface property. I started a thread many months back to clarify this issue, because my character is a slave and was able to bid on a Sencliff Shop.
This whole system seems really murky. Any time you're "allowed" to do something in game but not allowed to do it according to the rules as written, real players will ask themselves what's going on. Had I not started that thread, I may have found myself with a shop and chewed out by a DM for it.
My feedback is this: A slave should be able to attempt to bid on any property anywhere. If the rules forbid it, the slave should be told that the property is not available to slaves.
We should not have to ask ourselves: "I'm a pirate too, so I can bid in Sencliff, right?" or "Is Dis an exception to this rule?". We should be able to interact with the game rather than DMs and forums to advance our plot arcs.