I'm actually going to disagree with the common advice here about rental properties. That's effectively taking on another job; it might or might not turn out to be a well-paying one, but it's another job, and one you probably have little experience in. If you really want to invest in real estate to some degree, you can always invest in a REIT fund, preferably as one of several components of your investment strategy. And if you're not strongly attached to real estate, just invest in a good Vanguard index fund, with a balance of stocks and bonds depending on your desired risk level.
The only big open question is whether to pay off your house or invest that money. That's going to depend heavily on two things: how certain you are that you're not going to move soon, and how risk-averse you are. If you're not risk-averse, or you think you're likely to move in the next couple of years, you probably will make more money by investing the income and paying off the house normally, though you'll probably still want to make some extra principal payments every month to drastically reduce your total interest payment over the life of the loan. If you are risk-averse, however, you'll likely feel far more comfortable with your situation if you go ahead and pay off the house, eliminating your biggest monthly expense and getting you in a mindset for early retirement. You're in a position to retire very early; if you're not particularly attached to your job, plan on doing so.