The phrase relates to money.
You live once, you have the money and can afford the purchase right now. Down the line this may not be the case and all he may be able to afford is a bus pass.
One could argue that if down the line all he can afford is a bus pass, all the more reason to be cautious with money now to delay that situation. Maybe some of those people getting the bus are doing so because they were frivolous with money in their earlier years
