For 20W life insurance, you can find the premium based on your age. Let's assume 300 a year.
Then, you have basically 900 to invest.
And you assume a rate, from 7-9 percent annually based on historical SP 500 index return. See how many years you need to reach 20W. This is the calculator:
http://cgi.money.cnn.com/tools/savingscalc/savingscalc.html
Let me know the rate you need to reach 20W.