Keys to avoiding home rental scams
consumer.ftc.gov
consumer.ftc.gov
1) Signs at the rental property are forgeable, esp. for single-family homes. Don't trust them.
2) A good price might be a sign of a scam... or just the compromise you're looking for. (I currently rent at nearly 50% under market in exchange for taking care of maintenance/upkeep myself on an older property -- a deal I'm more than happy to accept, but admittedly not for everyone.)
3) Often government records are publicly available (although in California you have to go look them up on public access terminals in person; privacy laws prevent full disclosure online). Since many scams involve unaffiliated people representing themselves as the landlord and trying to collect background check fees, security deposits, etc., it's wise to find out who the property owner of record is with the gov't, and confirm that the person you're talking to is either that owner, or an authorized representative of the owner. If the owner is a company, you want to be able to corroborate through gov't info who's authorized to enter contracts on behalf of the company. And then don't be ashamed to ask the representative for photo ID. If they're legit, they'll respect that you're authenticating them; if they're not, they probably get upset or try to convince you it's not necessary, and you can walk away happy knowing you just avoided a scam.