What would be the best way to put about 50 html pages on a server so I can host them?

I've searched for days and have yet to find the solution, and I've never owned a webserver in my life up until now so this is all very very new to me.

These are the requirements:
They need to be able to register an account on the server, so it gives them upload abilities to the FTP server, but they can't write over someone elses shit

Each person who clicks upload gets their own folder on the server, for example

www.blahblah.com/files/theirnamehere/index.html
it only uploads HTML files from a folder which its destination is know, for example "app.path & /exported/html/" & "filenamehere.htm" so they wouldn't need to find the file on the computer.

it needs to be secure, IE: they can't edit the file before it's uploaded as it may or may not contain ads (havn't decided yet, but I need money to pay the 35$ a month for the server.) I don't want them to go into index, remove the ads, then click upload nor could they add code to the page and upload it compromising the server.

etc.

Sorry if this is really specific, but what would be the best way to do this? I was using an Inet and connecting that way but I feel this is a really unsafe thing to do for my server. That being said, is there another way to do this?

Thanks.