Shortly after getting engaged, we moved in together—to my condo.
Sharing space comes with some variations on sharing money too—the most common options seem to be:
One for All: All income goes in to one account, all expenses come out. All accounts are joint.
Totally Separate: Each person handles all of their own money; bills are split according to some formula (usually either 50/50 or proportionate to income). Either each partner handles different bills, or one partner handles them all and the other partner pays them.
Mixed Bag: Anywhere between the two above—some accounts are together, others are separate. Some expenses are joint, others are individual.