<prompt> Human: I have over 100k in cash sitting around in a bank account doing nothing but depreciating. Ive been sitting on it for awhile because I just dont know what to do with it. I have contemplated paying down my mortgage 4 interest rate. I could also put it into mutual funds, index funds, or individual stocks, but unsure if the market can sustain growth over the short term. It seems returns on bonds are all really low 2 for 5-10yr bonds. I dont need this money any time soon, but would still like to keep it somewhat liquid in case of another 2008 style meltdown; so not interested in IRA or 30yr bonds. What is the best option? Thanks.  <response>: Its tough to lose with a 4 guaranteed rate of return by paying your mortgage down.Thats not the most popular advice here, but damn I love my paid for house. 