TBH I was to... no big deal though.
Did I think that up myself? (apart from sounding a little condescending..) yes.
To elaborate a little for you.
Lets pretend that your money site is a gym, lets call it surfalot's Gym.
Any time you go there you are going to find 4 subsets of people, the Body-builders, the Housewives, the show off's and the young exec's.
These subsets of people, or groups of people all have similar interests and lit to talk about similar things, weights, bulking up, what oils to use when lathering up for the next big show.
The housewives on the other hand, all like to talk about diets, fads, looking slim and how they can manage the kids and driving around in their SUV's.
The young execs, like things like, yoga, stress relief and being able to competitivly run a marathon while closing a business deal.
and lastly the show off's like to talk about hair products, looking good for da ladiez and getting laid because they are so very good looking.
All these groups, while having dissimilar interests to each other, have a common theme and would in reality share links and sites, and social bookmarks amongst them selves.
But wait you say, Those interests are not really that dissimilar at all, they are just different thoughts on one topic... fitness.
Now how does the money site come into this?
Well, in reality these groups wouldn't actually be sending 5 million links back to your site from day one, they would be chatting amongst themselves, building the PR of their own sites, through interlinking and book-marking, then one day, they discover something really awesome on your site... a special, an offer or some sort of fitness how to that is really awesome...
That's when they all suddenly start sending you links back to your site, from their posts (anchor text) and that of course means that you as a good marketer, who monitors you links, would then start posting links back to your site in their comments...
then the offer is over, the groups go back to talking amongst themselves and your site gets kind of forgotten... until the next awesome post that they all want to talk about.
so you see how it's done?
As for posting volume, it will come down to how much you can spin really, and how much work you want to put in.