Are there any best practices for estimating web traffic based on an estimated user base?

Check out https://www.balancedpayments.com/ They are made for marketplaces. Airbnb CEO among others invested in them and they have some of the best pricing/payout fees. Also some good info on http://www.collaborativeconsumption.com/2013/10/08/online-marketplaces-are-hard/ One of Balanced Payments co-founders is writing this blog series on marketplaces.

You could try a "widget" on the lawyer's site which facilitates getting generic questions answered for free. The idea being that in each practice area, there might be a handful of questions that they get asked frequently, and would commit to answering one-time. It could be used to qualify the web visitor (always a good thing) while satisfying the visitor by providing them an answer. Of course, the challenge here is that most lawyers might only be comfortable providing such watered-down generic advice, that the answers themselves wouldn't be very useful. But this way, you could provide value to lawyers somewhat comfortable with online discourse, while building up content. With enough lawyers and content, you could then expand the service to build towards your larger vision. But as John has mentioned, many entrepreneurs have and are actively trying to win with this type of idea and have often struggled. CaseText is a recent YC grad that is doing some interesting work in this area. Happy to talk through your product implementation.

Focus on the more difficult side of the marketplace. For instance, if you think it'll be easier to get suppliers, then focus first on getting buyers - always be working on your toughest problem (aka your biggest risk). You'll find some great blogging on Marketplace and Platform topics here http://platformed.info (read the ebook too!)

I'm the CTO of https://3dagogo.com a marketplace of proven to print 3D designs. We look at the two sides differently. There's not a single customer. In our case you have designers and purchasers ( sometimes the same person can be both ). Cost and methods for acquiring designers are very different than those to attract purchasers. I would clearly separate the sides and come up with separate cost structures. In my opinion when you're looking at the marketplace from the purchaser perspective, the other side's acquisition costs can be seen as fixed marketing costs.

For four years, I was the marketing manager at Axial, a two sided marketplace that matches investors with companies looking to sell their businesses. We figured out the chicken and egg problem, then figured out how to market and sell each side in a way that scaled. When you think about building a two-sided marketplace it seems daunting, as your question reflects. It feels like you need to get everyone active all at once in order to create any value for anyone. But the truth is that you really only need to get one side engaged. The way I think about two-sided marketplaces is like a grocery store. A grocery store is one of the original two sided marketplaces: there’s a customer who needs fruit or milk or something else and there is a farmer who needs to sell fruit or milk. The grocery is the conduit between them, the two sided marketplace. If the farmer (or other vendor) can’t consistently sell their goods at the store, they’ll sell somewhere else. If the shopper doesn’t find the fruit or bread or other products they’re looking for on a regular basis, they’ll go somewhere else. The value of thinking about a two-sided marketplace like a grocery store is that it’s obvious who needs the product now and who is willing to wait awhile. The shopper has a very time limited window to buy the product - they’re going to be in the store for a half hour then they leave. If the product isn’t on the shelf, they’re not waiting for it. If the fruit is bad, they’re not buying it. The product on the shelf, on the other hand, can wait around. But each product does have a shelf life - some products, like canned foods, might last years while others, like fresh fruit or bread, might last only a couple of days. So, while the times need to match up, each side has different time requirements. In hacking a two-sided marketplace it helps tremendously to figure out which side of your market is the shopper and which side is the product. It’s not always obvious though. Sometimes what is being “bought” on your marketplace is actually the shopper. In the case of Axial, we were helping investors buy companies. It seems like the shopper is the investor. But it’s not - they’re actually the ones willing to wait around for the right company to come to them. The company being sold actually has a very short time frame to find the right buyer - usually a two week window in a well run sale process. On our marketplace, the two underlying assets were investor profiles and company profiles (to simplify everything). The investor profiles actually became our product on the shelf while the companies became the shoppers - even though it was the investors buying the companies. The investors were more willing to wait for the right company rather than the other way around. That insight helped us understand how to hack the marketplace to success. The side that is willing to wait around longer is almost always the easier side to collect. If you’re starting a grocery store, it’s always better to go talk to all the vendors and fill your store with product before you open it to shoppers. Leading shoppers through an empty store doesn’t meet their immediate need of needing to make dinner tonight. Talking to a farmer about the neighborhood customers you’ll have as soon as you open is a lot easier. And the farmer is more willing to have low sales at first in order to secure his spot on your shelves so his competitors don’t get the prime space he’s going to want later. If you think about Uber, which is clearly creating a two-sided marketplace of drivers and riders, they operate exactly the same way. In Uber’s case, the driver is the product on the shelf. The rider is the shopper. The drivers are willing to drive around for hours looking for rides. A rider will open the app, see if they can get a ride quickly, and if not will go to an alternative like Lyft, a taxi or the train/subway. That’s why Uber is spending so much money to acquire new drivers. They’ll pay drivers thousands to join, even buying them cars in some cases. They’ll sign limo drivers up as Uber Black drivers, convincing them that they’ll make as much or more than they are in the limo business. Then, when there is only UberX riders around and not enough drivers, Uber will eat the cost of paying an Uber Black driver to drive an UberX ride. Uber realizes that riders (shoppers) only use Uber (visit the store) if they’re confident good rides available when they want them (products they want are in stock and fresh). So Uber is hacking the product and letting it sit on the shelf (drivers driving around looking for rides) because that’s the only way to make sure they don’t lose to taxis or Lyft. I hope that gives you a framework to use as you think about growing or starting your two-sided marketplace. If you’d like to chat with me as you think through your marketplace, I’m available as an expert here on Clarity. I’m happy to make specific suggestions for how you can structure and grow your business. Good luck.