This idea seems best to me, just use google sheets or another spreadsheet document, each guild could have one, accessible to be viewed by anyone. That way, anyone can view how much money you have (so no cheating). A lot of sheets can even automatically update. I made an example here. All the guild leaders would have to do is every week add 1 week to each member, and the setting will multiply that by 10 for your amount of money. We could add another row so that amount spent would be there to, so it would subtract that. The people would just have to notify guild leaders when they spend allyverse money (we still need a better name for it).