I don't want to receive email from the for-sale group.

You can change your group notification settings for groups you are a member of, such as the "For-Sale" group, so you that you only receive a single email or no email at all for that group. (Be warned though, the best deals on For-Sale go quickly and often the digest email comes too late at the end of the day.)
Do NOT use this on the district group. Emails sent to the district group are meant to be important and received by everyone.
Choose your group membership settings.
Near the top left corner, click My Groups.
Find the name of the group you want to edit and click on that name. 
Near the upper right corner you will see the My Settings Icon. 
Click on Membership and email settings:
Click the drop-down menu on the line below your email address. You can choose any of the following options.

Don't send email updates: You won't get emails, but you can still see posts by logging in to Google Groups and clicking on that group. 
Send daily summaries: On days when people post to the group, you'll only get one email that includes every message that was sent.
Send combined updates: You'll get one email for every 25 posts to the group.
Send me an email for every new message: You'll get an email anytime someone posts to the group.
Remember to click on Save after you have made your selection.
Tip: If you post something and want to receive updates every time someone responds, check the box next to "Automatically subscribe me to email updates when I post to a topic."