3. Real Estate
If you are a real estate agent, you could create a post with a house/property image and ask users to enter their guessing price in the comment then you will message them the price for this house/property and trigger a conversation with them.
You could create a post which asks people if they are looking for a property within the next month Yes or No? If yes, you send them to a landing page that explains why you are a good choice that they should work with and automatically start a conversation with them. If no, you can ask them what type of real estate they wish to own?
Think of the different types of conversations you can create. Possibilities are endless.