Not all of the information filed with county clerks has been digitized and made available online. There are a few databases that make some of that information easily available online. In the absence of information being online, you will have to visit the County Clerk's office to browse through their many property books.
When searching for property records for a specific parcel of land, keep in mind that each new transaction affecting that property (deed transfers, mortgages, mortgage modifications, etc) is going to be recorded with the County Clerk in these books, which means that all of the information for a single property is going to be scattered throughout many books.
For verifying, supporting, or discrediting facts.
It's always a good idea to make sure that a professional's license is not only up-to-date, but also that there were never any lapses, disciplinary or other matters related to that license. This can help you to verify, support, or discredit facts.