Wouldn't it depend on the type of investment? Someone who fixes and flips isn't going to be happy with the same returns as someone who buys and holds. Even in the same category of investing, it would change. Someone who buys in a really nice suburb that has a manager in place isn't going to expect the same return as the guy who self manages a duplex in a war zone somewhere. What type of investing do you plan to do?
I don't own any yet, but when I look at properties and decide if its a good investment, I like to look at the rent to purchase price ratio. It's not the system I would use to actually purchase, but I like it for doing quick numbers. Once you know the market, you know what a certain unit will rent for, and you know roughly what the purchase price per unit should be in that area. In the same town, taxes should be similar, and insurance costs as well. I think you can determine fairly quickly if it even makes sense to look closer.