Could An Older Couple Achieve Financial Independence?

I know a couple who, at the ages of 59 and 61, have paid off all of their debts (except for some business-related credit card debt), have great credit scores, and own a paid-off home worth 575k. They have money invested in stocks (20k). They're in a solid financial situation, and they have a significant net worth that they plan to leverage into real estate investing, such as buying a house with low (3%-5%) downpayments and renting out the rooms, then using that equity to get a loan for another house, and so on. They also want to expand more with stocks. They have tried businesses before, gotten into lots of debt, one business worked out okay and helped them. Now they work hard to be educated and minimize taxes as much as possible on all their current and future possible incomes. They would like to eventually be able to stop working and live off passive income from stocks, real estate, etc. The husband still works a day job at a bus dealership, and he wants to one day be able to retire. They live in a LCOL area. How likely would this be in today's economy and factoring in their ages?