Bitcoin as a source of income or as an investment plan, which is better?
Depends on how good you are at earning Bitcoin through work, and how much money can you invest. If you have only $1,000, you won't make a lot of profit, because Bitcoin won't increase in value by 100 times. Investing $1,000 is worth it, but it won't change your life. But doubling or trippling a larger sum like $50,000 or $100,000 is a good investing move.
As for earning, if you're earning more money with BTC than with fiat doing the same job, then go for Bitcoin jobs. Otherwise work for fiat and buy Bitcoin with your earnings.
I'd agree with this point laid out, and in my opinion, bitcoin is an investment plan, for it has a promising future and most especially if you aren't investing larger amount into it