Non renwal lease form or letter?

[Marci Stein]

I’ve decided to sell and not renew my tenants lease. However, I would offer her the option of staying up to 60 days after her lease ends March 1 , 

since she has been there 10 years.

Anybody know if there is a formal 

non-renewal lease form 

I should send, a regular lease for 2 months, or simply a written letter of my own ?
Thanks!