How to add a roommate after a lease is made

[Mark Forest]

I have a tenant that can afford my SFH, but he told us he would eventually like to have a roommate. We will have him sign a one year lease. If he finds a suitable roommate that also meets our criteria how should I add him in? Do I write a new lease including the new person with whatever remaining months are on the original lease?

So for example he signs a lease now and in three months he gets a roommate. Do I then write a new lease for the two of them for nine months?