So "building a case" means what? Looking up the property in question and finding out who owns it for starters?
Building a case would mean having sufficient evidence to prosecute an individual that you want to charge with a crime.
A large part of that case building may hinge on the finding of evidence at a residence. But see, in America, you need something called a "warrant" in order to legally obtain that evidence. To get the warrant you need to convince something called a "judge" that there is a high probability the evidence is located at the residence you want to search.
Also in America, explaining to the judge that "This fellas neighbor done smelled weed before and is gettin' headaches somethin' awful lately" AIN'T GONNA [bleep]' CUT IT!
Anything sinking in yet?
Travis