So then I started to think about it and it brought me down the rabbit hole. 

Collins, Jackson Hole, etc.

The larger hole looks about an 8"x12" if they are standard 4"x4" tiles. 

Then all you have to do is find the point of intrusion, which could be hidden under a window sill (calking might help).I don't know that this is you problem but I do know how some older brick buildings were built and it seems like a possibility.Newer brick facads have weep holes at the bottom to exhaust water.Good luck!

If I go down a rabbit hole, I'll eventually learn how fridges work, so I figured I'd ask the BP peeps first. 

Just motivates landlords to find loop holes.

All 4 units are attached, one on top of the other on each side.Square ft: 850Scope of work:Entry WayPaint walls, ceiling, and trimFix doors to laundry closetInstall LVTInstall new front door locks rekeyableKitchenRecaulk countertopPaint walls, ceiling, and trimFix back door lightInstall new light fixtureInstall new outlet and covers whiteInstall new kitchen faucetRemove carpetInstall LVTInstall new stoveFamily roomPaint walls, ceiling, and trimRemove carpetInstall LVTBathroomRemove flooringInstall LVTRecaulk vanity and tubInstall new faucetInstall new toiletFix towel barsRemove shower door (allow tenant to install curtain)Bedroom 1Remove carpetPaint walls ceiling and trimFix closet doors to workInstall LVTBedroom 2Remove carpetPaint walls, ceiling, and trimFix walls (holes)Fix closet doors to workInstall LVTRe-hang door (door should be in garage, but new one may be needed)GeneralInstall new door hardwareGarage door inspection (garage door opener doesn’t work)Bug bomb unitClean unit when doneInstall new outlets and switch make them whiteCheck windows to operateOtherHVAC (furnace needs new filter)Dumpster serviceWasher box hookups are looseSnake sewer line

After doing the clean out I was making a punch list and noticed an unusual hole in the wall ... we popped out what looked like a 9MM slug.

Somehow it would need to stay in the hole and also be weathertight. 

Then look at the "holes" where you see very few storage locations if any.