Fourth Amendment to the United States Constitution is the part of the Bill of Rights that prohibits unreasonable searches and seizures and requires any warrant to be judicially sanctioned and supported by probable cause.
In Katz v. United States (1967), the Supreme Court held that its protections, such as the warrant requirement, extend to the privacy of individuals as well as physical locations.
The Court has defined a series of exceptions for consent searches, motor vehicle searches, evidence in plain view, exigent circumstances, border searches, and other situations.
While most people think that the forth amendment only applies to searches inside buildings it actually applies to Curtilage areas also.
Curtilage is the area, usually enclosed, encompassing the grounds and buildings immediately surrounding a home that is used in the daily activities of domestic life. If however someone was to walk to your front door and knock and saw something on the way that would be admissible in court without a search warrant.
So unless someone is above the constitution they do not have the power to search in your home or curtilage area.
That said do you really want them to estimate what you have and tax you that way?