Could you disclose how much one can make on airbnb? I have a 2 bedroom apartment and sometimes, when I leave on vacation, I would like to rent it out.

Depends on your location. Do an airbnb search in your area to get an idea. I just made up a price for mine, and when I was getting tons of requests for it, raised the prices to slow them to a manageable rate. Living in SF doesn't hurt.

In SF you could easily rent out a spare room in a 2br apartment for $65-120 per night depending on the quality. I typically do 10 days a month at $100 per night. Sometimes I hire a cleaner, and buy some wine/snacks/breakfast for guests but it's been very easy and I love doing it. Disclaimer: I work for Airbnb.

Easiest way to figure that out is to check what's available in your area on Airbnb and see what equivalent places are going for.