Different uncertain circumstances can hinder one from having numerous source of income but if one is in a better situation whereby they're fit or healthy enough to have numerous source of income then the better for such folks cause more source of income means more discretionary for investment and more funds to take care of other expenses too and more discretionary means a higher rate of accumulation to yield more profits, that's why when an investor has held for so many years, many about a decade or so it would be wise for the person to take some profits and create another source of income, maybe a business that would generate more income and discretionary to accumulate more Bitcoin and add value to their portfolio.
Earning money from multiple places is great idea if you are healthy enough to do so. More income means more money for you to invest and cover your expenses. This helps you build your wealth faster. If investor has held asset for a very long time like ten years it can be smart choice to sell portion of it. They can then use that money to start new business. This new business can become another source of income providing even more funds to invest and grow their portfolio.
But people should not wait to have that multiple income stream first before they think about buying Bitcoin. Having single stream is I think enough as long as they have discretionary income left which they can use for their Bitcoin investment.
Although what you have said is right but I think its not easy as what you have said since its not automatic that once you build a business you immediately became successful. Since for me having many of those things will bring lots of stress especially if you can't handle those businesses so well. So for me before those situation happen its better that we already have good position and continuously buying Bitcoin and lets take another step once everything settled out and no other stressful factors that might give us any problem in life.