The Poor House states "if you have no gold at the end of your turn receive one gold". The Tax Collector collects one gold at the end of the turn if you build. So, if build but have no gold at the end of the turn, do you collect from the Poor House then give that to the Tax Collector or just keep the gold from the Poor House?

According to the fan collected clarifications here: http://www.boardgamegeek.com/thread/406296/the-faq-to-end-all-faqs-work-in-progress the Tax Collector is first then the Poor House kicks in. So if you had no gold, he gets nothing and you get the charity. If you had one gold, he takes it and then you get the charity.

In this case the source is apparently a clarification in a German edition of the game.