One of my closest friends who also happens to be a competitor did a Groupon last year. In general it was a horrible experience for him. He sold 150 deals. Regular price was $199 for exterior softwash up to 1800 SQF. Additional square footage ( 10 cent per foot) , concrete, decks, , etc were all an up-charge. Deal was sold at $99, so he got $60 per deal.
Quickly realized that the coupon shoppers were in general very cheap. Was able to upsell/upgrade very, very few customers. If fact even had several larger homes that had purchased the deal and the buyers would only allow him to clean the front side of the home, since it fell above the 1800 SQF maximum, rather than pay a few extra dollars and get the whole house cleaned.
Here were the positives:
1) May keep 10-15 % of the customers as repeats
2) Had 15% of buyers not claim their voucher, so he was paid for those, even though he did not do the work.
3) It brought him HUGE SEO juice.
It was a huge pain and he'll never do it again!