You can start in crypto without investing any money, but to earn a decent amount, you would need to spend a lot of time. It's simple maths really, if you earn more in your day job, then best to spend majority of your time on that and invest what you can afford. You can always do a few bounties or airdrops to start you off while you're earning in the real world. You can definitely start in cryptocurrency without investing any money, just don't expect to become a millionaire any time soon. Good luck.