Forms required for Tenants before purchase

[Stuart Cairns]

I am purchasing my first duplex in July as long as the appraisal comes back OK. I read a couple of years ago that, before signing the transfer of ownership to have the tenants sign a form, which nullifies the previous landlords lease agreement. I cannot remember the name of that form and what its benefits are to the Landlord. Does anyone know what I am referring to?