The normals bro, invest as much as you're willing to lose. You may not be working in your seventies, so I'll not be talking about income here but retirement benefits. You could carve out money you'll not be needing in like 5 years time or more and invest into Bitcoin. I may not recommend holding for a very long term since you're old and age is a factor to consider when holding Bitcoin.
5 years is long-term and your investments is likely to be profitable by then and you can choose to sell off or keep holding.
Omor you see that line wey I make bold, e no dey correct abeg, na gambling get that scope. Why I go know say I go lose money and you dey tell me to still invest and even get mind call am investment? Risk wey dey untop bitcoin no reach where we go talk say person go lose him money kpata kpata, the price fit drop and you lose small if you no fit wait but that one no mean say all your owo don vamus. Me and u know say na only time e go take bitcoin to bounce back when e go down, so we should tell people wey wan invest to only put money wey them fit leave for bitcoin for as long as e go take to see better profit. Any body wey me dey tell about bitcoin, I dey tell am to buy and keep am for 10 years, say by then the investment go give am better gain.
You suppose dey aware say Bitcoin no get guarantee, although the risk dey very small, but nobody get any guarantee for their investment. I go still advise you make you no dey give people assurance for their Bitcoin investment. If the investment no go well, them go dey on your neck. Allow people to decide what they do, just introduce them to Bitcoin, and reason them wetin dey obtainable, but never give them any guarantee.
These old people suppose take as minimal risks as possible, that's why they should buy Bitcoin only with money they can afford to lose.