If you're building a Networking site, Cheat
Elgg - Open Source Social Networking Platform.
Yes, you can code stuff from the ground up all over again, or just use a Public Domain Package that's already available.
The Problem you're going to have is Funds.
You really do get what you pay for.
Yes there are Free host out there that control what you can post, ect.
You can get a Domain Name (Example pgp-protector.com is One of My Domain Names) for around $10 a year, but this doesn't include hosting.
Hosting on a shared server can start as low as $2-$5 a Month when you pay by the year, and can go up.
As you start out your site, unless you've got quite a few people lined up, you're not going to have a lot of traffic (visitors) so shared hosting is a good way to get started, but as your ministry grows, you'll eventually outgrow shared hosting and require more Server Power / Bandwidth, then you're looking at $$$. But my that time hopefully you can get donations from your Members.