This is the most popular "free" route. WordPress is free, and the BuddyPress plugin instantly adds Facebook-like features: member profiles, activity streams, user groups, and private messaging.
Here is a comprehensive guide on how to build, customize, and launch your own for free. 1. Choose Your "Engine" (The Platform) create a social website like facebook for free free
Building it is only half the battle. To keep it free and sustainable: This is the most popular "free" route