Dear Don,
I just heard today that you have found yourself a new job and are going back to being employed soon! I want to offer my congratulations to you on this occasion. One of us had to find someone willing to let us work and I am happy you found that person. I hear the company is a good place to work and I know you will do well there with your abilities and experience.
If you need any assistance during your first few days such as a ride, or someone to care for your pets while they learn the new schedule please do not hesitate to call me for the favor.
Sincerely,