Welcome to the community, Harinda!
This is a great subject area and very interesting for HTC to delve deeper into. I saw you also posted in Business model innovation, which is good.
We just created the first MVP of our Community Hub, and it is still quite empty there, but I think the at the Docs section for Sustainable business we should start to create an overview of alternative models.
I really like Aral Balkan’s take on Small Tech. The thread also mentions zebrasunite.com, which could a great place to get more info too.
Regarding advertising there are: