As I mentioned in the starting, I stayed for a month in Bir Billing as a Zostel volunteer. As a result, my stay, food, and sightseeing was free for the duration.
You can do the same by heading to the Zostel website and searching under their Volunteer opportunities. However, make sure that you are free for at least 4 weeks before applying because that is the minimum amount of time needed to become a volunteer.
Also, during your volunteering period, you will have 5-6 hours of work to do. After that you are free to explore as you wish.
Apart from Zostel, you also have the option to volunteer at Dharmalaya Institute for at least a month in which your stay and food will be free. Also, you will get an experience of how it feels to live in a sustainable environment.
One thing to note is that if you are going for a volunteering opportunity in Dharmalaya, then you would need to work and help them out 5-7 hours a day. After that, you are free to roam around.
Rent an Appartment/P.G.
You can also take an appartment/P.G. here for 4000 - 5000 INR but then expect to spend around 9000 - 10000 for your 1-month stay in Bir Billing.
What and Where to Eat in Bir Billing