In Citadels, when do characters get the extra gold from their colour?

Question

In the Citadels one of the benefits of your characters is receiving extra gold from buildings of the same colour. For example, each green building gives one extra gold to the merchant.

I am wondering; does this bonus start immediately at the beginning of your turn, or can one trigger the bonus at will? In the last example it could be beneficial to build a new building before triggering the bonus so one gets an extra gold piece.

Also, do you have to trigger the whole ability at once or can you split it up? This is especially important for the merchant who already gets 1 gold by default as special ability.

Answer 1

You can trigger the bonus before or after building. This means you can either build a building with your existing gold, then trigger the gold collection, OR trigger the gold collection, and use that gold to pay for a new building.

What you cannot do is gain some of the gold, build the building, and gain the extra gold from building that building.

To answer the edit, you always get the merchant's one gold before building. You can still choose to take his 1 gold per green either before or after building.

Answer 2

This ability is called 'taxing'. You may do it once per turn (which means it can't be split up). You may tax before or after you build a district.