Multifamily rentals are a good way to do this.. You can land some nice preferred stocks paying fairly secure divys too. You need to do your research
http://www.biggerpockets.com is a good place to start.
I have a duplex town house, so I rent one out and it basically pays for my home expenses. I also bought another investment property, a 6 unit in a decent area in my city for 500k, put 20% down. Pulls in around 3k a month after all expenses on average.
My investments built up over the years. I have four accounts. A retirement account from my job, a Roth IRA, emergency savings, and a regular investment account. Retirement accounts are 90% stocks, 10% bonds. Investment account is more 70% bonds (earning 3.5% tax free annually or 4%+ taxable), and the rest in an S & P 500 fund. All investments throw off between 1000 - 1500 a month on average. Took some time, to build up.
I check my investment accounts and look for new opportunities weekly. My non-retirement account is heavy on bonds due to the impending correction. Once we correct 20% +, I'd go long stocks again. I will not retire for another 30 years or so. That is why my retirement accounts are heavy the S & P 500 and Total Stock Market.
As for the investment properties, if you can find a good deal, then you go for it. I started with my duplex and slowly learned how to manage things. However, for the 6 unit I bought, I did hire a well known property manager. There's 34+ people living in that building. They call for stupid sh it. Less headaches and he takes care of a lot of things. If I had more time (and patients), I'd manage it myself.