I made some homes for my personal use but I did not want them to be just walked into. So I made a trader, that sells keys. Realistic enough for me. Problem: The NPC does not sell keys that have a value. They sell keys that don't have any value for 0 gold but not the very expensive keys I made for these homes.

I tried different classes (trader service, pawnbroker and savant service) and different AI's (autocalculate stats and handmade stats). I always made sure, that "sells/buys misc items" was checked.

i don't want a solution with scripts I'm just too lazy for it. How can I solve this?

Make 1st NPC sell, like, deeds to houses, 2nd - to give keys if PC has deeds - via dialogue. That's how it's done in Houses And Apartments mod, IIRC. You still have to do some scripting though.

So there is no possibility to sell keys via trade window? Meh...

give key a 0.01 weight

Yeah I'm pretty sure that this works.

If the above one doesnt work i have an idea though it would require some simple scripting, try creating a pouch which can be sold by the trader at some good cost and attach a script to the pouch which upon opening in inventory will remove itself and add the key it is meant for to the inventory and i am pretty sure a script for that already exist in default game (The packages given Caius Cosades work the same ways dont they?) Hope it helps.

Did not (they had a 1.0 weight already, changing to 0.01 did not help) Thanks for the suggestion nonetheless
But I'm so darn lazy I just skip it and hide those &%$§ keys somewhere

strange, it worked for me (gave a new key to Fargoth). Did you try from a fresh new game?

Always check mods like that. A friend gave a esp to me that he made with keys. They work. Giving his NPC my keys does not (still sells his own). It does not help anything like changing the containing chest or give the NPC the key directly in his inventory.