I think it would be a good money maker and I would do 3 things to really make it successful:
1. There are a TON of dating websites on the market today so your offline campaign will have to be just as strong as your online marketing. I would try to partner up with any business or sponsor you could possibly partner with to gain market exposure. Look for venues and businesses that would compliment your website. Maybe you can link up with Meetup.com and sponsor some of their singles groups. Maybe giving away a free month if you use meetup.com in the promotional box.
2. Find something that no one else is doing. That is going to be hard because most of the larger sites are doing everything right now. I can`t off the top of my head think of anything. Maybe you can do a group dating thing or include a forum in your dating site. Maybe you can import some of google lab products into your site.
3. Give a absolutely free month (but make sure you take their credit card and charge them at the begin of the next month) to do everything. Most dating sites let you sign up but then you have to pay to get to see your matches or your emails or both. This is fustrating. If you make it free for a month they will more likely sign up and even though you will get a lot of cancellations, some will forget and some won`t cancel at all. I think its a better model than the pay to play model most dating websites offer. I think they offer it mostly because most people never really find a date on those sites.
4. This is a bit unethical but all of the major dating sites have done it. Fill your site with models and stand ins. You want to make your site look like its well established and lots of good looking people using it. If you only have 2 people in California who are looking for a date then you`re not going to have much business. Filling them with models will increase your business because people will think people are using your site.
5. Another idea is to link up with all the major dating sites and do something like what orbitz and hotwire does for the airline business. Make your site a gateway site to all the other major dating sites. If you can do something like that with 3 or 4 major dating sites then you will do very well for yourself.
Those are some of my ideas.
I hope it helps.