A topic from AEG's L5R CCG Rules forum, copied for Oracle of the Void from a copy of the forum saved in October 2015, so pages it didn't save are missing. Players' names are left out; the rules officials are named. Rulings are as they stood on these dates; later rulings, the rulebooks and the Rules Archive may differ.
Let's say that Seppun Horai is in play. There is a barley farm in a province and a personality that costs 4 gold in another province.
Is it legal to bow your bamboo harvester to pay for the barley farm, react with Horai's ability since you are paying for a farm, and then use that 4 gold from Horai's reaction to purchase your 4 gold personality?
No it is not legal. Assuming this is the Dynasty Phase, the cards in provinces are not bought simultaneously but one at a time, and a player may not be produce surplus Gold in order to spare it for another purchase (see Dynasty Phase and Gold production). Seppun Horai may produce 4 Gold only to pay for a farm.