Ownership
Who owns what share
Usually proportional to the deposit, but it does not have to be. Whatever you agree, put it in writing before closing.
Agree it before you offer
The awkward conversations
are cheaper up front.
Co-buying works fine until something changes. Every question below is far easier to answer before the money moves.
Exit
What happens if one wants out
A buyout formula agreed now beats a negotiation during a fallout. Decide how the price gets set and how long the other has to raise it.
Costs
Who pays for what, monthly
Mortgage, taxes, insurance, repairs. Split them the same way as ownership, or differently — but decide, and write it down.