@eaglejarl @Velorien @OliWhail
Let us say that the average D-rank mission is 3 hours, and that Because Teambuilding the average team that
would take a D rank takes two a day. That's 40 ryo per day, let's say 6 days a week for 240 ryo a week. I assume that this is sufficient for a genin to survive alone with food and cheap (but not slum level) housing. Because I don't know, inflation.
I would say that the threat multiplier would best be adjusted by the Hokage -- or someone he trusts to estimate threat -- accordingly to the skill level required to complete the misison safely. So if something required an estimated 30 tac move/combat/awareness, it'd be, say, a 4x multiplier? Just throwing numbers out there.
20 * 8 (for a total of 24 hours) * 2 (for two days) = 320 Ryo minimum for a C rank mission, but that doesn't account for the additional risk. Let's say that the basic C rank provides a... let's call it a 2x Threat multiplier. So 640 minimum ryo per person for a max length C rank mission.
160 (24 hours) * 14 (max length) * 4 (average threat multiplier) = 8960 ryo per person for a max length B rank mission
160 (24 hours) * 25 (length of "milk run" intel-gathering mission) * 6 (multiplier for being involved in an engagement with a jounin) = 24,000 Ryo per person (96,000 to the clan's coffers, 24,000 to Akane, 24,000 to Minami's family)
e: You could probably pull inspiration from the rulebooks for Shadowrun runs on this, actually.