To calculate how much you need to save every month to earn
$30,000 per year in interest for retirement, we need to make a few assumptions.
Let's assume that you plan to retire in 30 years, and you want to have a
retirement fund of $1 million by then. We'll also assume a 6% annual return on
your investments.

Using these assumptions, we can use the following formula to
calculate the monthly savings needed to earn $30,000 per year in interest:

PV = FV / (1 + r)^n where PV is the present value (or the
amount you need to save), FV is the future value (or $1 million), r is the
annual interest rate (or 6%), and n is the number of years until retirement (or
30).

Solving for PV, we get:

PV = FV / (1 + r)^n PV = $1,000,000 / (1 + 0.06)^30 PV =
$226,145.67

So you would need to save $226,145.67 over the next 30 years
to have a retirement fund of $1 million with a 6% annual return. To earn
$30,000 per year in interest from that fund, you would need to divide that
amount by the number of months in a year and get:

$30,000 / 12 = $2,500

Therefore, you would need to save $2,500 every month for the
next 30 years to earn $30,000 per year in interest for retirement.