You didn't say, but assuming you're in the US...

In addition to the things already mentioned, decide who gets the tax breaks for real estate taxes and interest. If it's shared, make sure that there is some sort of legal document acceptable to the IRS. BTW, if your bank/lender insists that taxes and home owners insurance have to be paid to them (in an "escrow" account, so they can play with your money) find another bank. Make regular (group) payments into your own account for this, and have a party at the end of the year with the interest.

Consider some sort of regular payment by all occupants into a home maintenance fund. I'd suggest that this account have at least enough in it all times to replace the hot water heater when it blows up at 2:00 am on a Sunday morning in February.