This is always the first question of newbies without capital and this question is not a bad one. I feel sorry for the rude comments you received because I have been there myself. To answer your question, there are two ways to earn bitcoin without investing money: bounty campaign and air drops. In the first one, although you won't be investing money, you need to invest time to rank up your account because campaigns accepts high rank accounts and it will take time and effort to do so. The latter is by airdrop, it's easier but not much assurance that you will earn. You can do your research on both methods and make a choice. Personally I prefer campaigns. Good Luck!