There are many alternatives to help you buy more properties. It all depends on your specific situation. If you have equity in your home, you can use that to obtain down payment money to purchase another home. You can also use a self directed IRA. If you have an IRA that is not performing as well for you as you'd like, roll it into a self directed account and then you can use it to buy investment property. Make sure, however, that you learn all the rules of doing this. The IRS governs the laws of using IRA's and you have to be very careful not to get yourself into trouble. I've recently bought an investment property through my self directed account. It's a great way to diversify.
You can also partner with people or find a local real estate investment club to join and get some ideas from other investors.
Be very careful out there, Real estate can be a great way to earn extra income. It can also be devistating if you don't know what you're doing. Do some research and find a good real estate agent who specializes in investment properties. Many normal agents don't understand the numbers and how to chose a good investment property. If you'd like, I'd be happy to help you find one in the St Louis area.
Let me know 303-913-9129 or firstname.lastname@example.org