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.
Re: this comment:
Clan discount and Invest are different things, and can be used together. So you can increase GC by the Invest cost and reduce GC by 2 thanks to clan discount.
Emphasis mine.
Gives the impression that Invest is part of the card's cost and not a separate cost. If so, does that mean that a single holding could pay for both a personality and their invest cost in one go (as opposed to it being a separate cost of X gold)?
That implication was unintended, I'll clarify my answer. Of course Invest is a separate cost and must be paid separately.