I am a lawyer in CT and practice in this area.  A person does not go from being a visitor to a tenant.  You are either one or the other.  A tenant has a right to occupy property under certain terms for a certain period of time so long as rent is received. A visitor has no right to occupy the property and may be asked to lease at any time and does not have to pay rent.  If you are going to enter into a lease, i suggest that you put something in writing identifying the property, the amount of monthly rent and the the term of the tenancy.  it the person just wants to stay on a month to month basis, then agree to a certain rental amount for each month.