This can be done only after closing has taken place.

It sounds as though the listing agent is being unreasonable.  The agent may not have even asked the sellers if it was okay to show and just made a lazy decision.

If the property is still tenant occupied and the tenants do not wish to be disturbed, I can sort of see that.

Is it currently occupied? If so, maybe not, based on the owner's feelings; if it is vacant, definitely so.

I have done this as a buyer.

Lise Howe - I think it's too early for the buyer to start bringin in the tenants. Yes, it is understood why the buyer is buying, however, if that is inconveniet to the sellers, I'd rather tell my buyer to wait. Now if seller cooperates, nothing wrong in it. After all we have to work for WIN-WIN. 

Lise,

If the property is vacant, why not?  Sometimes people like to make their importance felt, perhaps this is the case here. A

I think it depends if the property is vacant or not. If it's vacant and the buyer's agent will attend, why not?

I agree with Roy Kelley on this question. With an agent present, if my client is amenable and it does not disturb existing tenants then yes.

If the tenant is represented by an agent and the property is vacant, I would allow the agent to show the property. If the property is occupied, I would ask the owners if they wish to allow the showings.

I would not allow the purchaser to conduct showings without an agent.

Bringing in potential tenants that seller knows nothing about is a risk not worth taking. The buyer has already seen the unit, and there are probably pics in mls his potential tenant could look at. The listing agent could jsut be relaying the instructions of the sellers. What happens if the potential tenant falls down the steps or trips and falls and bangs his head against corner of counter? The buyer doesn't own it yet, and shouldn't be acting like he does. They can wait another 2 weeks.

Hi Lisa -- it doesn't sound like an unreasonable request but maybe there is more to the situation that is not in your question.   As Bill Dandridge comment asks -- occupied or not -- can make a difference as well as the owner's permission.  

I would talk to the listing agent and see what might put him/her and the seller more at ease with allowing a one time showing.  

My guess is Listing Agent is afraid the deal might fall apart if the prospective tenants do not like the property.

I agree with Bill but even if occupied you could just set it up like a regular showing. We show property under contract all the time in case of a fall out. I would have the buyer's agent take the buyer and their prospective renter to the property, after identifying the renter and ensuring they know the property may not be available.