I own a website. Is it easy to turn it to a web hosting server? Is it profitable?

You need to know a lot about servers, server management/administration, keeping them secure etc. Then you will need to have a good site with proper billing and customer support applications, then you will need to have employees to help your clients.

So now see it for yourself if you can sustain all this and have profit.

I think he is interested in running own web hosting service (not server) according to the section.
Iа so I suggest you start with affiliate program to look how things going. Then reseller account and then dedicated server.
But I highly recomend you join into any web hosting related affiliate programm.

Find a Reseller account, its a cheap way to manage a webhosting company with no hardware costs, for need for server knowledge, there are plenty around.

You can get one for about £20/$40 per month, with good diskspace/bandwidth limits and service features.. You can make good money doing that and when you get big enough, and understand Hosting more, you can make the move to your own servers.