I hope this helps!
this is quite interesting question because there is no concrete answers for it.. it is all depending on the listing contract that you have had with the agent who listed your property and got it rented.. I for example do not charge for any lease renewals however if the tenants bought the home then I do ask for my commission.
my advice is that you call the listing agent and explain the situation, many of them will be reasonable to work with and I would think if they are a true good agents and/or sales people they will see the benefits of getting your business again vs. making a small commission now..
please let me know if you need any real estate help. my cell is 630-329-5000.
Re/Max of Naperville
It depends on your agreement. If the agent procured someone to lease and then purchase, in most cases you may have to pay a commission every year and also on the sale.
Something that many people don't understand is that you need to agree on a sales price "now". Even if it's in 2 years.