Unlimited components, lockpick, parts and crowbar.

[Won't blame you]

There's a guy in garage. He's always outside protecting his father. He asks you for meds. On the first trade, you give him medications and get the sawblade and some else, maybe. Go on to the top of the house and use sawblade on the back side of house. Get as much as you want from the basement and go back home. You go there again later, whenever feels like. You give him a piece of wood ( Piece of anything, actually ), he gives you unlimited components, lockpick, parts and crowbar. It seems those 4 things cost zero somehow. Don't abuse it though.

[FreedomFighter]

Semi-Detachted House work too, if it spawn trader. Basically, you steal their merchandise, not their main supply for survive.

[BananaDealer]

There's a bug in the vendors/traders. Sometimes they all offer you pretty much their entire store for a drop of water. Other times you'll be lucky to trade 4 shotguns for a peace of wood...
I'm not sure how you can force this bug though...