When designing an online business, so may people focus on the largest possible market. It’s easy to see why. After all, if you’re potential marketplace is the entire world, you only need a tiny slice to succeed.

That works if you’re selling on eBay, but it’s not a sound approach for online dating sites. Remember that you are selling access to profiles, and you only bring value to the table if I find promising profiles.

So if your dating site invites members from around the world, you could easily get thousands of members, and still not have critical mass in any one geographic area. The result is a “dead” site, where nothing happens.

It’s far better to restrict your membership to a tight area — a single country, state, or even city. You’ll be more focused on your efforts, have an easier time leveraging search engine optimization and search engine marketing, be able to take advantage of local media, and — most importantly — be able to build critical mass in a single location to start with.

1,500 members from around the world is useless: your members still won’t be able to connect.

But if you have 1,500 members all from New England, for example, you’re starting to get traction.

Reserve a couple of nights per week, a Sunday morning here, and a day from vacation time there. It’s never been cheaper or faster to build a web startup, it’s never been more possible to do it as a side-business.

Sure, we’ve all read about Markus Frind running the free Plentyoffish.com out of his apartment, and raking in millions through advertising. But he’s a great example of a guy who was in the right place at the right time (not to mention a great entrepreneur).

Just because he made it work, doesn’t mean there’s an endless amount of marketspace for other free, general-interest sites.

The majority of small, niche dating sites need revenue to grow and sustain themselves. Now, if you found a few million in VC funding, you can stop reading.

For the rest of us, there’s no shame in charging for a valuable service. That doesn’t mean a general site that does the same as all the other sites out there…

But a solid niche site that solves its members’ problems well and has found a market that isn’t swamped, can and should charge for its services.

Don’t worry that charging will slow your growth: in fact, charging a reasonable fee can actually spur growth, because it lets you launch an affiliate program, which in turn can open the flood gates to new opportunities.