The main problem I see with buying or selling gambling websites in todays market are:
1. As a buyer it doesn’t make sense to pay more than 6 months income, especially considering most websites are reliant on seo. Over 5 years ago I bought a website that was top 10 in google for online casinos and 2 weeks later it was delisted.
2. As a seller you would have to be crazy to sell a website for 6 months income. I might consider it if you offered me 2 years income, but looking back, if I sold my websites for 2 years income 5 years ago it would have been pretty silly.
I do know some affiliates who are horrible at seo, but they still do well from buying others peoples websites and offering less than a years income, so there is a huge market place for this.