Selling a house with a tenant on a yearly lease?

[Kris Lippi]

I have a woman who is looking to list her house that is currently rented to a tenant. The lease doesn't end until October of 2015. In the brief call I had with her, she said she has in her lease terms that she can sell the property during the lease and the tenants would have to move out. 

I will ask her to send me the lease before putting on the market for me to review, however, I just wanted to ask the question here as to whether or not anyone else has had experience with this and is it even legal?