3-site directory solution RFP

Good morning.

We are in the process of 'blueskying' a niche industry 'yellow pages' - style directory webring. Our first venture will be three related websites offering listings for three areas of a single industry, with practicioners in the retail, service, and supply side of this industry to be represented.

We have looked at PHPMyDirectory, and it has a number of positive attributes. However, it is not diverse enough to meet all our (at this point theoretical) needs.. and we are certain that Drupal would be. However, we have been unable at this point to find a 'directory' module, per se, so are coming here in hopes of gaining some interest.

At it's most basic, the solution would have 3-5 levels of subscription, ranging from free to premium, with increasing levels of service at higher levels (completely conventional) At the highest levels, however, we would allow content creation outside the actual 'customer record'... news, blog, contribute to the "book". Not a bonafide admin position, but certainly an über-subsriber.

The solution differs significantly from the classic directory model in one significant way: we wish to list geographically, rather than by trade/business. In other words: province > region > city would be the standard navigation protocol. However, not entirely: there are minor differences, and small product ranges, within each business. We have not yet solved the concept here... ideas?

In any event, we are looking for a solution that would offer a common database with three domains using it. Each domain would serve a different corner of the niche, but all are within a related business niche.

We would respectfully request ideas, samples, and approximate quotes on the cost to implement this concept.