We use the standard We Buy Houses sign with a local number that goes straight to voicemail. The voicemail then tells them a little about what we do, we also tell them that we are investors and we expect to make a profit so we need to buy at a discount or pretty sweet terms. Those that are interested leave a message those that want full price all cash...Don't. This weeds out the leads without having to pay for expensive "live operators".
NOTE: Sellers appreiciate when your upfront with them. Don't try to hide the fact that your in this to make money, but don't be rude about it either.
In my opinion putting a URL on a bandit sign is a BAD idea so I don't do it. The bandit sign gives them one way of contacting us, this makes it better to track the actual results of the bandit signs.
Personally I think bandit signs are a good cheap way to get the phone to start ringing. But remember, 1 is the most dangerous number in marketing, so make sure you have other "fishing poles" in the water.
Hope that helps.