Think of returns are being inversely propositional to effort. No effort is very passive, but the returns are not awesome. Great returns are available, but in my experience, they are not passive. There's due diligence on the front, or management on the backend, to make a great return happen.

CD's / Money market accounts yield small returns, and are very passive.
Less passive are annuity products. You have to do your homework on the front end, but it can yield well.

Hard money lending is great. It will be work if there is a default, but the returns are very good, and it's collateralized debt, meaning you gain an asset if you're the first on the loan and there is a default. The way it becomes non-passive is if you collect.

If you start talking about business, then passive probably isn't going to happen (at least not long term). It's going to need active management. The returns are generally much better, but it's not passive.

I hope that helps!