Bitcoin the only decentralised cryptocurrency that is dependable and guaranteed return on investment which is undeniably the truth about it.
You are not guaranteed ROI, people who asks questions like this usually have zero knowledge of Bitcoin, and they are closer to losing every sat they have than making ROI on them.
Bitcoin as a source of income or as an investment plan, which is better?
(It has many advantages and disadvantages, but advantages superceeds the disadvantages). Putting the disadvantages into consideration and as a person that want to lower their risk of loss, will bitcoin be suitable as a source of income (not fully, like part-time job), or investing fully in them and wait for a large profit since many users here in the forum foresee it that, at halving the price always go up above the current All time high.
Bitcoin is money, money cannot be a source of income, you do something to earn money, and that thing you do is the source of income, thus what it is it that you do/want to do to earn Bitcoin (money)?
Bitcoin as an investment plan? It is your Bitcoins (your coins), do whatsoever is suitable for you with it!