Passive Income vs Equivalent Savings Calculator will show you how much you would have to have in savings to produce a set passive income.  

Just enter the passive amount for the month and the annual estimate will be displayed below that entry.  Then slide the interest rate to the desired interest rate.  The average long term interest rate is about 5% or .05 and that is the default setting.  Then just read the amount displayed at the bottom which shows how much you would need in savings - to produce the monthly passive income that you entered.

Then ask yourself - was it easier to produce that passive income - or would it be easier to save the amount that is displayed in the Equivalent Savings Amount box?