House Upgrade

[msalley50]

I am level 20, I have purchased some houses, but when I go to the NPC to buy upgrades I can't because it is not an option.

[EASY PETE]

You were scammed

[Saizo]

You have to go to a certain trader and open the trading window like you would buy normally.
Those upgrades look like items (letters) and are inside the merchant's inventory.

[The Minted Lady]

You have to visit your house first, then you get the quest to see the trader about getting the upgrades.

If you're playing a thief, I will also point out that some house upgrades can be found in other NPC's houses. It can save you money to just go in and take them instead. There's at least one in one of the houses in the temple district of the Imperial City, and the Surillie Brothers' house has two in Skingrad. The upgrades are city specific, so you can't steal them from Skingrad and get them to work in Bravil, for example.

[msalley50]

I have gone to the house in bruma, then to the seller i was told about by countess carvain, buying upgrades for my house wasn't an option.

[Ammikaameri]

The upgrades are items you buy. Not a different dialogue option.
As with all other items you can only buy them when the shop is open.