Thank you, some thoughtful suggestions there.My friend was living in a shared house with a few people, but her fiance also lived there and shared the rent equally. Once she got married and they moved out on their own (which all happened at the same time) her centrelink benefits dropped massively. There was no interim payment available, no warning of how much it would drop, etc, it just dropped by over 50% from one week to the next.
If her husband owns property she might not be eligible for centrelink benefits that are based on asset tests (doesn't affect the family tax benefits though - that is based on his income).
I suggest they move in together when they get married in either house - if his doesn't sell, then they should rent it out if they don't want to live there. Or they could break the lease on her current place and move into his place. I don't see why they need to keep 2 places going for long. And if they do, then it's just part of the costs of moving, so they just need to take that into account when they sell & buy that they need money to cover that period when they have 2 houses for a bit.