Reddit reviews Talking to Children About Divorce: A Parent's Guide to Healthy Communication at Each Stage of Divorce: Expert Advice for Kids' Emotional Recovery

Have as much as possible of a complete and stable plan for them ready to be laid out BEFORE you tell him. "May" need to sell the house is not something you want to tell him. Either you're going to sell the house or you aren't.

If it is in any way possible, get as many details of the divorce laid out in advance before telling them. Figure out custody/visitation, where each parent is going to live, etc.

Then, honestly its the same-old, same-old "Mommy and Daddy both love you guys SO VERY MUCH, but we don't love each other anymore. Sometimes mom's and dad's fight a lot and decide it is better for them not to be married anymore. That is what your father and I have decided is best for our family, for mom and dad to live apart. You're going to spend X days here with me, and Y days with your father."

Allow them to ask questions, and answer them in an age appropriate way. If you aren't prepared to answer the question, don't be afraid to tell them that you don't know, or that you'll get back to them on that after you think about it.

Pick up a few books from the library about how to talk to kids about divorce, or honestly just google for some articles. Here's a suggestion from Amazon. This google search alone comes up with a ton of good articles about what to say/what not to say. How to answer questions, etc.