Elderly tenant, non-tenant son has taken over finances

[Dan B.]

I just purchased an investment property. One of the tenants is elderly. I was just informed that her son has taken over her finances. There was no lease agreement in place when I purchased. The tenant wants to stay, but I'm not sure how to draft the lease. Has anyone ever done a lease where the tenant living there will not be signing the lease? Do i put the elderly mother's name as the tenant and just have her son sign it?