Hey there!
When you have messages with business, you're usually asking for something. That something can be money, or it can be for a deal, or for a sale. Whatever it may be, in your message, you want to get straight to the point. It should not be long, and it shouldn't have a lot of unnecessary things in it because if you don't get to your point the whole thing may be overlooked and your effort will go to waste.
It should be conversational and casual, and you should make sure what you're saying is clear as ice.
Hope this helps!