Can I give investors a cash return on their investments, instead of company equity?

You're talking about a loan then. Of course you can, but its an entirely different kind of investment. While investing for equity means that the investors share your failure, loans would likely to require collateral (mortgage on the real estate in question, most likely). You can then offer even lower rates of return, 100% is quite a lot.

The thing is that investors don't do loans, usually. Banks do loans. Investors want equity because they expect your business to grow far beyond your current ability to repay (which is what is important when asking for a loan). Those who invested in Facebook 5 years ago, or Google 10 years ago, got back much much more than 100%.

You may find investors that like these terms, but perhaps you shouldn't like them yourself.

Say you get five investors, they give you one million which you put in the bank as a nice asset. You immediately have two million liability, plus you need to spend some of the original million on buying properties, incurring costs.

I don't see how you'll ever make money for yourself, as the investors would obviously want preference when it came to distributing profits. Also, most (all?) the property bubbles around the world are burst, so 100% returns are no longer possible in sensible timescales. Ten years ago in London, you could have done 100% over three years quite easily, but now, the whole market is going sideways.

Maybe I'm missing something, but I don't see how you'll fill the massive black hole of liabilities, e.g. one million plus in my example.

In the end, issuing shares (equity) is a way to protect you, as it shares the risk, and the reward (if any). Business ventures have been conducted in this way for hundreds (thousands?) of years, so there must be a reason why people do that.

http://en.wikipedia.org/wiki/Company