That sounds madly illegal?
Unless one helps himself to the house contents, or does other Bad Things, walking through unlocked dwellings will get you at most a slap on the wrist.
Much like someone open carrying a gun is seen as potentially a few seconds away from committing a Very Bad Crime, so is someone walking around your house uninvited.
Not exactly legal.
But even stepping back, I suspect walking around and jiggling random peoples’ doorknobs to see if they’re unlocked is probably illegal.
Edit: We went through the process for everything, including having a provider ship us a back-up solution to pentest. My desk became everyone's favourite place in the building :P
I do some bug bounty hunting for fun, and just yesterday I Googled a weird snippet of frontend code from a major corporation, found the matching backend code in a blog post, and saw a bug in it. Alas, not a bug that could be used for anything interesting this time.