No matter whomever uses your dungeon, you will find globs of lube in the stupidest places. The method of finding said globs will be in mid session reaching for a something that you would, for all practical reasons, believe to be clean. Then you must hold your composure because you are the domme and your sub is right there.

Take a damage/theft deposit, have them sign something releasing you from liability, and include cleaning everything in the fee.
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I've broken all my toys. Would you like to be broken?