One of the ways to make extra money is to sell leads
You can make money free, online, by selling leads, or referrals. This is where you partner with a business which pays you on a cost-per-action (CPA) basis, where the action is carried out by your website visitors that you refer to them. It is similar to affiliate marketing.
The difference is, the partner can be an offline, or another online business. And the CPA can be:
pay-per-click: when your visitor clicks a link in your webpage and lands on their website, or
pay-per-lead: when the visitor you direct to their website fills in a form or subscribes to a service, or
pay-per-sale: when your visitor buys from the business you refer him to.
Let's say you know of an area with tourist potential. You could sell leads by getting a commission on any sales made when you refer visitors to motels and restaurants and car rental companies in that area. Or take cruise ship tours, which are booming. You can liaise with cruise ship lines to refer visitors to them, perhaps even doing the initial online booking. But you would need to find and partner with such offline businesses yourself.
For online businesses, websites such as cj.com and directleads.com list merchants willing to pay you for sending visitors who subscribe or sign up. Onresponse.com even pays for leads who take up free product trials and offers! Since your visitors don't need to actually purchase anything from them, conversion rates (i.e. the percentage of visitors who carry out the desired action so that you get paid) can be much higher than standard pay-per-sale programs.
For Directleads and Onresponse, commissions per action range from $0.07 to $15, with most being between $1 to $2. Before you can sell leads to them however, these two programs do require that you have your own website, with upwards of 100 visitors per day.
We recommend that you sell referrals as one of the ways to make extra money on top of the main business of your website, so as to get multiple income streams from it.
With a website, you can also make money free, online, by selling ad space on it. Or, if you want to look at the other ways as well... go back to Ways to Make Money Online.