Assuming your tenant has an assured shorthold tenancy and the fixed period (usually 6 months) has expired and there is the provision for the property to be viewed or to be sold, which are both standard conditions of the tenancy and should be in the tenancy agreement, this is not a problem and is quite common. Offer the house for sale with vacant possession upon completion and give the tenant two months notice to leave when you exchange contracts but make sure you have at least three months between exchange and completion.
It can go wrong and the tenant does not leave when they should and you have to go to court for possession, which you should get if you follow the correct procedure, but it takes time, if this concerns you give the tenant notice to leave and do not offer the house for sale until they have gone, but you may lose income by doing this.