You need to calculate the net present value of the total expected income. $40,000 in the year of 2050 has not has the same value of $40,000 in 2005. Using 5% discount rate, the NPV is about $701,836, using all 單身老貓's assumptions. However, $40,000 a year may not be an acceptable salary for a temp, and there are many other factors that may make the damage much smaller.