8x13 flue with a gap like that is just asking for trouble. Honestly, I've seen some real humdingers in the field, but one that stuck with me was a chimney in Lakewood where they used a flat cap on a round flue. @jennifer358 mentioned slapping mesh on it, but that's a temporary fix at best. With that inch gap on two sides, birds will nest in there by spring and rain will rot the clay liner in a year or two. Your neighbor needs a proper fabricated cap with an 8x13 flange, and he should measure the flue himself next time before letting anyone touch it.

Safe is boring, man" - tell that to your bank account when the Mustang's transmission gives out at 80k miles. You're hauling cleaning supplies, not groceries, and that Civic's got a backseat that actually folds down flat. Plus that $80 a month difference adds up to almost a grand a year you can spend on literally anything more fun than a car payment.

Same thing happened to mine a few months back. Fixed it the exact same way, just a quick clean of the float switch with some vinegar. Kinda wild how such a tiny bit of gunk can cause a whole flood like that.

12 years of bad crimps, oof, feel that pain lmao.

Oh man, I read somewhere that people are way less likely to take cash that's locked up (like the physical act of unlocking makes it feel more like stealing). Sounds like you found a solid workaround for your roommate problem though.