Most ad exchanges wait until they're paid by the brands that are running ads through them before they pay you. In other words, you don't get paid until they get paid. So don't be surprised if you don't get a check from them for 90 to 120 days. Read the insertion orders carefully before you sign them to understand how long you're likely to wait to get paid. Oh, and measuring exactly how many ads have been served is notoriously difficult. Over the course of a month, you can check your online dashboards to see how much revenue you're making, but these are really just a guide. The ad exchanges will let you know how much they actually owe you at the end of each month, and for the most part, you'll have to accept their calculations.