In any lease situation you should have a good relationship with...

In any lease situation you should have a good relationship with the tenant (not as a friend) so if you decide to sell the property it is a simple process to just give the tenant money for inconvenience and costs, as long as they present the house well for the sale, don't be greedy, a good sitting tenant can add value to the price.
If they are a bad tenant you will have grounds to kick them out anyway

It takes two for any deal.