I'm curious how you do, or how you would want to do if you were in a relationship. So this question isn't limited to people in a bed sharing partner relationship, aka cohabiting or married couples, but also single people. How do you organize the household economy? Or how would you want to organize the household economy if you had a girlfriend/boyfriend/wife/husband?
Some people have completely shared family economy, where all the money goes into a joint account and everything is paid jointly. Purchase decisions is mostly made jointly etc.
At the other end we find completely separated finances, where you only pay your half of the common household expenses and use the rest of one's earned money as one feels like.
Inbetween these two there are variations. For example, to divide up the money proportionally to income once everything in common is paid. Or to share 50-50, or any other distribution.