Finding a good rental manager is what usually had guys up nights tearing their hair out, though. There are more than a few guys in the Navy nowadays who got into rental properties during the boom and lost their hat, ass and overcoat.
As vick says, though, that stuff is long-range and you won't have the time, energy or money to fuck around with it once you start deploying. Becoming an Amway whore is one of the quickest ways to lose friends in the squadron (and potentially get in some ethics trouble if you start pushing it on the E's - it's happened).
If you've got a little time and cash to play with right now, sign up for e*trade or something and play the market a bit. Lots of bargain stocks out there these days. As always, though, Vegas rules: don't put up more than you can afford to lose, and know when to walk away from a losing table.