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.
I think it will take them about 3 to 4 years to fully understand the bitcoin and they must have a very high skill as well as dedication if they do not want to make their way of finding bitcoin to nowhere