It's very difficult to answer your question, but...
As I said, this is a very difficult question to answer. Think what you can do yourself. Are you able to prepare any of the content yourself? Do you have any knowledge in any school subjects? If so, then you could prepare content in one subject, promote the website and then look for volounteers to participate in your project and post their films.
Unles you have a spare milion bucks you can invest and pay profesionals do the job for you.
I would say it depends on how hard you are willing to work - are you open to learn anything and everything and only hire others for services when you absolutely must? How much time do you have - can you work on this full time or just on weekends? Your main expense could be content creation (since content IS your product), but if that's your strength you have a shot at running a low cost operation while building traffic and a brand. If you can't be the main content contributor I would suggest finding a partner who can (or to supplement your expertise) because product (content) development will end up being a long term and ongoing expense. It also depends on the type of content you need to produce - text, images, video, etc. You could find free tools for some tasks, but professional software will require spending some money (a few hundred dollars).
If you plan to start slow and post on few topics rather then launch with many categories, you could try using a blog platform or some free web site templates that many hosting companies will offer as you are building out your content offering. Just pick a good domain name, ideally with a solid keyword in the name. Register a few domains if you find a few usable names that are available, just ownership will cost you $10-12 per domain per year. If you use a blog platform like WordPress you can point your domain to your blog for $12/year until you are ready to launch a site with navigation, faq, terms, ads, etc.
Sorry if my post was angling at doing it on the cheap, rather than giving you info on cost. Need more info in order to advise any further.