Revenue Models and advertising revenue

I am new to making/managing websites. Infact, I haven't even dipped my toe in yet.

I have an idea with a potential client base in Millions(education related).

The content is being provided by a team of specialists on the subject.

We plan to:

1- Make a part of the websites(videos) absolutely free.

I am wondering whether this in itself can make us some ad revenue and how to figure out potential revenue.

2- After the videos, the content and one-on-one interaction etc are a selling point.

3- Potential ad clients: Schools, colleges, study abroad centers etc.

This part I am not completely sure about. The number of people coming to the site will be a factor or the number of subscriber base?

I don't have the funds to start this venture on my own. I am looking to get the numbers in place to start working on the funding part.

I hope someone would be willing to help get me off the ground on the above points.

Most important among all this is can a education based video website be run just on ad revenue without revenue from any other source?

Please help with your wealth of experience.

Thanks