Owning a server for social network site

I'm looking to start a niche social network site. I estimate at least 20k members. My question is this. I've been looking into getting a dedicated server. They average like 150$ a month from companies like godaddy etc. So I looked into buying one and found them for like $1500 and up. I have also heard stories of hosting companies screwing people over and things so I thought it might be best to buy a server. So here is what I am wondering. It seems actually cheaper over the course of 3 years to own a server and run it.
If I have Verizon Fios and a server is that pretty much all I need or do the hosting companies provide you with something more?

Yeah, they provide you with the comfort of knowing that when you're drunk as fuck at a bar 30 minutes away from your house and your power goes out, you don't have to worry about getting home to fix it... amongst other things.

outsource it its less of a hassle once you have the traffic if you really want to then yeah otherwise i dont think its worth the hassle you can always scale up and down and your internet connection fios or cable or dsl is not the same is a professional data center by godaddy or a company like rackspace

verizon blocks port 80 so unless you know what your doing you cant set up a server. Plus they require you to have business internet to be allowed to run a server. Just use dreamhost VPS 150 MB should be plenty to start until you get bigger and they allow red 5 and fms so you can even set up video chat

your home internet speed is not even close to what you'd get in a datacenter - plus (if they are set up right) a datacenter will have all kinds of electricity backups, and internet connectivity backups (in other words: more than one internet connection, in case one goes down) and security: once you have 20k worth of personal information, the easiest way to steal it would be to just bust into your house (why bother hacking) - a datacenter has real security.

Even if you think you'll get 20k subscribers, you should start smaller and scale up as you need to (many hosts can handle this)

As for your host screwing you over - just make sure you make daily backups of your site...
You can get a dedicated server for less than 150 (much less if you manage it yourself) but why not start out with a VPS? Don't spend the money while you are still building up.