How does Yoritomo Sensei interact with holdings with a printed gold cost of 0? (Do they cost 0 or 1)
What about prosperous village with 5 personalities in play (0 or 1?) With 6?
Yoritomo Sensei vs. Holdings
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.
Yoritomo Sensei's trait reads: Your Gold-producing Holdings enter play for you paying 1 less Gold, to a minimum of 1.
And the rules on reducing stats "to a minimum" state:
A: Apply all current bonuses and penalties that are not restricted by “to a minimum” or “to a maximum”.
B: Apply all current bonuses and penalties that are restricted by “to a minimum” or “to a maximum”; applying maximum-restricted bonuses first in ascending order of the maximum's numerical value, then minimum-restricted penalties in descending order of the minimum's value. The restriction means that if that particular bonus or penalty would take the stat below that minimum or above that maximum, its amount is reduced until it is only enough to reach that minimum or maximum. [ADDED 13 Jun 2012]
This means: a) If the holding has a base cost of 0, it will ignore Yoritomo Sensei's trait because the stat is already below the minimum. The holding's Gold Cost remains 0. b) Prosperous Village with 5 Personalities in play will still cost 1 gold, because Prosperous Village applies first (step A in the quote above) and reduces Gold Cost to 1, then in step B Yoritomo Sensei tries to apply can't reduce the holding's cost below 1 due to the minimum. c) Prosperous Village with 6 Personalities in play will cost 0, because you first apply reductions without a minimum (step A in the quote above) and then Yoritomo Sensei tries to apply (step B) but since the Gold Cost is already below its minimum, it has no effects.
Note: It works differently when the minimum (or maximum) isn't linked to a stat modification eg Growing Hostilities will cause your Prosperous Villages to cost 1 gold even if you have 6 or more Personalities in play, because that minimum would apply in step D, not B.
TL;dr If the holding's Gold Cost is already below the minimum either because its base Gold Cost is 0 or because some other Gold Cost reduction lowers it to 0, the "to a minimum" won't raise it back to 1.