You will need to find some decent rental RE to purchase first.
RE is not like stocks. You can't (ok, REITs, sorta) just buy a bunch of random pieces of property and expect to do well. RE is (at least at the beginning) a full time job, and then it's running a part-time business. You make your money by finding really good deals and doing a lot of work up front.
If you want set/forget, just buy index funds. If you want to do RE, start reading and researching and set yourself up to be ready to pull the trigger (this could mean having some extra downpayment cash around, having your credit score up nice and high, making sure your debt/income ratio will let you qualify for a mortgage, etc).
There are not a lot of markets in the US where I would buy residential RE right now, though.
-W