Depends on a number of factors.
- Age of site/domain?
- Recurring revenue, like membership site, or affiliate?
- Traffic and referrals?
9-12 months revenue is a fair gauge. However, if the revenue is recurring, and you can show a track record of it (longer than a few months) you may be able to push for 12-18 months.
In the end it will come down to what he is willing to let it go for, and the other person will buy it for. You will have plenty of people who will low ball, however, I have found that as long as you are not desperate. You will eventually get your asking price. It may take 2-3 months, but you'll get it.
