The Declaration in the POS for the
DVC Resorts provides (sec. 13.2 in the BWV declarations; section number may differ in others):
"All leasing or rental agreements relating to the use, occupancy and possession of any Vacation Home must be in writing and must set forth an acknowledgment and consent on the part of the lessee-sublessee-tenant to use, occupy and possess such Vacation Home in conformance and compliance with the provisions of this Declaration, as well as the Articles of Incorpation, Bylaws, the Condominium Rules and Regulations and the rules and regulations of the Disney Vacation Club. In the event the Owner or Cotenant fails to secure a written lease or rental agreement , the Associationshall have the right to require the lessee-sublessee-tenant, prior to thew lease-sublessee-tenant's use, occupancy or, possession of any Vacation Home, to execute an acknowledgement to use and occupy the rental or leased Vacation Home in conformance with the Condominium Documents. Any lease or rental agreement shall be deemed to contain a provision requiring that any sums due to the Association as assessmenrts must be deducted from the gross rentals and paid directly to the Association."
In other words, a written agreement is actually required, although it is likely a requirement overlooked by many, and the penalty for not having one is for the association, if it desires, to force the tenant to acknowledge he will be bound by all applicable rules and regulations.
I have seen form agreements online but do not remember where. It is likely better to have a written agreement, particularly to cover such things as payment and what happens if something goes wrong. Moreover, there are some things you may want to point out in a contract to avoid unpleasant issues, e.g., have agreement that the tenant is not to request an upgrade to a better/larger room when he checks in, because what usually happens if the upgrade is given is that your account gets charged for the extra points needed for the better room.