After some research I know that there are two primary tenant database services in use, NTD and TICA. They do not share data, so to be thorough you should check both. At the very least, the advice goes, you should check the DB that is prevalent in your state. Apparently in Queensland TICA is the most popular. There are a multitude of services where a self-managing landlord can access NTD for a small fee. But I can't find anyone who'll sell a TICA search. Can I obtain ad hoc TICA searches from anywhere?