There are many things that can go wrong. Having a plan and educating yourself on your market and the strategy or strategies you intend to use is very important. To begin purchasing property with out a clear plan will eventually lead you into trouble.
You will want to know the market you are investing in as well, if you don't then you will want to find qualified advisers to help you.
Leverage is a good thing. To much leverage usually leads to negative cash flow. Some may try this with the hope of future appreciation making up the difference. I n my opinion this is a poor strategy especially sense there are properties that will cash flow.
You will need to have at least some money to invest with. There are some strategies that require significantly less money, but some money is necessary. If you are without money, you will need something else that you can offer to a partnership.
When you start out you will want to learn the legal environment you are working in. Find good agreements and contracts and in y opinion you should have a lawyer review your contracts to insure that they are enforceable and cover the risks associated with the deal you are involving yourself in.