Since, the food cost may vary according to the individual I haven't considered it in the cost. But to give you an estimation food might cost you around 1000-2000Rs.
Tip: If you have a tent and a sleeping bag you can cut the cost even more.
To solve the problem of having to use toilet and security, approch the homestay or hotel owners and ask them if you could pitch the tent in their garden and use the common washroom, for this you can pay them 50-100Rs. but don't pay beyond 150Rs. This will pull your cost down to just 2000Rs. (excluding food)