Earning a bitcoin in this time without investment is really hard, its value is rapidly increasing in overseas markets. However, you can still earn bitcoin through social media programs or signature campaigns.
It is not hard to earn a bitcoin in a month or two for skillful people. If they have some special skills then they from this forum can get some orders for the work and can earn that money from this single platform easily. While for non skilled people it is really very hard to earn without any investment.
That is the problem; not everyone skillful to earn 1 btc per month, even investment project is a secret door which only few lucky people who knows it.
Then, mostly people suggest to trading altcoins, but you need big capital first and enough knowledge to avoid loss.
Furthermore, if you know how to get it ; will you tell people how to get it? We should learn and develop ourselves skills to make it, right. There is no a definite answer for everyone.