[paulddraper]

Your proposed parallel is backwards. The house is for sale to the buyer; the employee's time and skills are for sale to the employer.

So those question would be more like "How much do you pay other employees?" or "How much have you offered other candidates?"

You can ask those questions. Some employers are upfront, even posting salary ranges in the job ad itself. Other employers will decline to share that information.

Either side can reveal as much or as little information about their employment history as they choose. Curtailing freedoms is a heavy-handed act, despite the theoretical advantage to candidates.