As a merchant, I did Groupon deals a few times. Most of the time, clients are nice. Sometimes they can be rude & vicious.
I am a Massage therapist. I opened my studio in 2014. My first deal was $29 swedish (Groupon takes your regular prices & sells it for 50% off & merchant keeps half of $29). Your first deal they collect 50%. If you sell alot, your new deals after the first deal, you can keep more. You need to negotiate with Groupon. The more services you offer, the more % u keep. It works well for service industry. Doesn't work well for products.