sorry for the frequent post, running into a lot of issues playing.. Ten towers lets you play a card from an opponents discard pile once per round AS THOUGH IT WERE IN YOUR HAND. Does that mean I have to pay the 2 gold penalty for it being an out of house card if it has a gold cost, like a character, since im playing it as though its in my hand?

Yes. The operative word here is "play", because whenever you play a card (instead of putting it into play) you need to apply all relevant penalties. The "as if it were in your hand" merely makes playing the card possible, because you cannot play a card from anywhere but your hand.