Consider:
Proper description of the property in the agent’s listings (don’t call a 2 bedroom house a 3 bedroom just because some room may somehow be converted)
Honesty and fiduciary duty involves proper disclosure, don’t try to hide issues, they can come back to bite you later (such as illegal or unpermitted additions or conversions)
If agents don’t know the answer to a question, admit it, and go look for the answer – don’t wing it

Good luck, it’s a tough business