Putting a house that is up for sale for rent

[Elizabeth Z.]

I currently have a house for sale but there hasn't been many showings. I decided to put the house for rent since I only have 2 more months on the contract with my realtor. I figured, that way I have time to find good tenants. I have done this before and has worked out. I simply let the tenants know the house if for sale and do a month to month contract with 30 day notice if the sale goes under contract. Also a 48 hour notice if there will be a showing. I also give them the option of staying if the house doesn't sell and doing a longer lease. Well today my realtor informed me that I can't  do that and will have to take the house of the market if I'm going to be advertising it for rent. Is there a new rule stating this that I'm not aware of? What are your thought on this matter.