Co-tenant leaving, other wants to stay, not sure how to act

[Nick Jensen]

We (wife and I) have two single guys renting a house from us. They are on a month-to-month on the same agreement. One of the guys is moving out and gave us notice at the beginning of the month that he'd have his stuff out by the end of the month. The other guy wants to stay. He's been trying to find a housemate but not having any luck. 

Staying Guy is aware that he'll be responsible for the entire rent next month regardless if he can find a housemate. He's also aware that we'll be requiring a new agreement starting March 1.

Today Staying Guy asked us to help him find a housemate. We don't feel it's our duty to play matchmaker for him. Is it time to have The Conversation with him that if he can't pay rent he'll have to move out by the end of the month?