Therefore, do you think that a source of income must be steady enough for years, before one can be financially free or rich or very wealthy, depending on the source(s) of income?
Financial stability is your ability to have enough funds to cover your basic needs and also invest. Needs are insatiable so you will always need a steady income to be financially stable. For you to be able to maintain a rich lifestyle you need to have a steady source of income.
Even if every source of income you have don’t have to be steady, having at least a few reliable ones will definitely make you feel more secure. Steady inflow of income gives you the opportunity to manage your expenses, to invest for the future, and weather through any financial storms that may surface.
Some people live a lavish lifestyle that they would need more sources of income to finance it. The amount an individual needs steadily will depend on his expenditure.