tenant notification of intent to sell

i have a friend who owns a three flat in chicago, illinois (cook county) - he is interested in selling the building and has current tenants. is he obligated to inform his tenants of his intent to sell or once the building is sold - does the buyer inform the tenants. if he has to notify his tenants is there a form letter he should send or can you tell us what should be included in the letter. thank you very much for your time and attention.

[HomeGuru]

He is not obligated to inform the tenants unless required by local law. Once the property closes, both Buyer and Seller should inform the tenants especially with respect to the security deposits.