it's not a secret actually ,If you browse the forum regularly you can surely find some ways to earn Bitcoin.Your earning amount depends on your skills,If you have some skills like trading, programming, development etc then you will be able to earn more than 0.1 BTC per week.Again, Without investment you can earn up to 0.1 BTC per week by joining a signature campaign.
That is not a realistic number for most users here, since you will probably need to be in the highest paying campaign and your account will need to be legendary to have such a pay and even that may not be possible because it will depend on your commitment to comment in the forum.
I can point you to 5 accounts owned by one person with different signatures but mostly Sr,member and above in the last 5 pages of this thread.
They are committed to post on the forum no doubt but they don't care if they are posting something useful or different or atleast their own opinions in short sentences.
Easily with 5 or more accounts you could earn more than 0.1
BTC weekly but at what cost?
I always try to keep my posts as short and useful as I can to avoid wasting people's time.
That is possible but that would not help the forum in general, you are making money but all the ideas are just coming from you. You can enjoy that while you last but the moment you get caught violating the rules, you opportunity to join the signature campaign will be eliminated.