Hello,
I live in Brazil and I've been working with website development for the past six years. For your project, I'd use an open-source solution called BuddyPress.
It would allow us to focus on the website's features/design and deliver a great user experience. Besides, it'd keep the costs low.
I'd love to hear more details about what you'd like on your social network and I'm looking forward to work on this project as it looks very challenging.
Best Regards,
Will