How far in advance of a realestate agent have to give before showing an occupied dwelling?

I rent a homeowner trying to sell. I was told that the realestate agent to give me 24 hours. notice to bring someone on a watch. However, twice this week, called at the last minute to carry someone in the house. What we notice prior to people round my house?

24 hours, or you may have a long duration, usually between 8.5 days.