Facebook now has a billion users, but those looking to connect on the social network might have to shell out some serious cash if they want their friends to notice their posts. “This morning, there are more than one billion people using Facebook actively each month,” CEO Mark Zuckerberg posted Thursday. “If you’re reading this: thank you for giving me and my little team the honor of serving you.” Though the accomplishment marks a major milestone for Facebook, the company is still struggling to stabilize its image after its disappointing IPO in May, and is openly pursuing more ways to bring in revenue. One of the ways Facebook — Which has always gone by the slogan “It’s free and always will be”  — is monetizing its platform is by allowing users to pay to promote their posts. The site has been testing the feature for months around the world, starting with users in New Zealand and expanding to 20 countries. On Wednesday, Facebook announced it was bringing Promoted Posts to the U.S.