Investing in Bitcoin does not depend on income. If someone wants to invest in Bitcoin properly, there are some things that must be in it. He must have a basic understanding of Bitcoin, he must have desire and patience, and he must have discretionary income. Let's say a person's income is very high but after his own and family's expenses, he does not have much money left. This means that he does not have discretionary income, so it would not be right for him to invest in Bitcoin. On the other hand, if a person earns very little money but it turns out that after spending all his expenses, he has some money left at the end of the day, then he can invest with that money. Whether the discretionary income can be more or less will depend on the person's income and expenses. If it is less, he will invest with a small amount of money following DCA and if it is more, he will start investing with more money according to his position. However, he must invest with discretionary income. This will allow him to continue his investment activities for a long time and the possibility of making profits in the future will be much higher.
To be a successful Bitcoin investor you need to understand financial management and have a discretionary fund, this are the two things that you need to succeed in it's long term investment. No doubt DCA method is the best strategy to remain focused in buying and hodl for atleast between 4 to 10 years. Remove basic expenses from your income, push the rest into your discretionary funds account and work out a budget that will take care of the funds in it. Make buying Bitcoin a priority from your discretionary funds and be disciplined to always buy when money drops into it no matter what current price is.
DCA is most effective strategy for non traders, people can withstand the volatility of the market by doing that strategy. This will became more effective if the person doing it always have available funds or discretionary income to cover up their investment for long term purposes.
No doubt this is best strategy especially if they aim to invest on Bitcoin then target to HODL for 4 - 10 years or maybe even more longer than this timelines. People need to have good discipline since this is long term commitment but for sure everything is provably worth it since Bitcoin potential is so big. So chance to earn is huge compare if they trade their Bitcoin for short term only.