If you are trying to build a site like youtube you will need SEVERAL dedicated servers and plenty of money backing you i read an article about youtube in Inc or smart money or one of those mags they had millions in startup money to get it going...
The combination of video downloads and forums is a particularly bad one as far as apache web server optimization goes. Since you are talking about starting at $10/mo, I assume you want to start small with little investment and grow. You might want to start with a VPS account. There are a couple of advantages to a VPS. One is that your host isn't going to unexpectedly shut down your site for resource usage and tell you to get lost. 400GB for $10? Ask them if they allow adult. If they don't thats a good sign they don't actually expect you to use all that cheap bandwidth and will be looking for a way to show you the door as an unprofitable customer. (If your users are going to be able to upload content, you are going to be easy to get rid of between copyright, adult, and CPU usage.) For his kind of thing, you need to check the TOS and AUP very carefully. Another advantage to VPS is that with VPS software, such as virtuozzo, your host can add more resources to your server or move your server to a different machine very easily with a minimum of downtime. Since they are moving the server image, there is less (no?) chance of things getting lost or broken in the move. I use the VPS at ServInt. They have good service. Their low end package starts at $49/mo and they can move your server up until you only share the server with one other user (Deuce), or have the server to yourself (solo). The Deuce and Solo products are not listed on the front page, but you can see the details in the private VPS forum. One thing that you want to make sure that you do is to divide your hosting so that your videos and images are served from their own domain, dedicated for that purpose. something like media.youclone.com. Even if the same web server handles all the traffic, you will need this segregation to grow. So, lets say that you start with a $49/mo VPS and grow. At some point, you will have to expand. At that point, I would recommend considering Zend Platform. I think its $250 if your business makes less that $250k/yr. Zend Platform has specific optimizations for downloading video: Then, as you grow, you can move up the VPS ladder until its easier or cheaper to jump to a dedicated. Jumping from a single dedicated to multiple is a different post. This is a pretty easy way you could scale, sub-dedicated. Profitably? I don't know about that.