Can ad revenue sustain this model?

Hello, I'm currently in the planning stages of a simple idea.. It's nothing major, I'm just a student and just want to get my feet wet.. However, as I think more and more about it, I'm more and more worried about one thing..
The idea is that this web site should fulfill user's need, so I'm not talking about solving problems.. More like entertainment.. Everything will be free and would only revolve around reading/writing/posting comments etc..
Now, let's say I'm that lucky and start getting insane amount of traffic from day 1. My first idea was to use something like Heroku, start with free plan and then as traffic increases I start making more and more money off ads and then I can pay for more bandwidth etc and still get some profit..
TL,DR; I have a insane amount of traffic on my site, only way to get paid are ads.. Can I use profit from ads to pay for bandwidth and still get some for myself? The users will mostly read/engage into fun stories and there will be no affiliate marketing what so ever.. Also this site should be for all people, so no adult content.. Thanks!

I wouldn't worry about the exact balance of traffic and ad revenue you can reach until after you launch. Because frankly, until you launch, you have no idea how your traffic will look like.

First of all, the most likely outcome is that you don't get much traffic: your site is just not that exciting for users. So worries about ad revenue becomes moot.

Second of all, even if your traffic starts growing, you will probably pivot and tweak things many times to hit the sweet spot. Think of Justin.tv giving up on random videos and focusing on gaming. There is no way they would have known until it happened to them.

In the end, once your traffic looks good, there will be plenty of people (investors and consultants) happy to show you how to make money with it. The challenge is to get the traffic.

In the meantime, you can play with some basic math. 1000 visitors can net you one dollar (estimate can be off by 10X either way). Estimate your hosting costs and see if it's sustainable.