Work through each section honestly. The questions that give you pause are the ones worth spending time on before you commit.
The financial foundation
We've run the actual numbers, not just rough estimates
Monthly savings, equity positions, break-even on any conversion. The calculator makes this concrete.
The arrangement makes financial sense for both parties, not just one
If the numbers only work for one party, the other will feel it — and the arrangement will be fragile.
We've agreed how costs will be split and what that looks like monthly
Not "roughly" — specifically. Which costs are shared, which are individual, and on what basis.
Party B's contributions build real equity, not just subsidise Party A's mortgage
If Party B is paying below-market rent with no equity stake, the arrangement helps Party A and leaves Party B where they started.
We have a plan for what happens if one party's financial situation changes significantly
Job loss, illness, a new baby. The arrangement should be able to flex without falling apart.
The legal structure
We've chosen the right ownership structure (tenants in common, not joint tenancy)
For most multigenerational arrangements, tenants in common with defined shares is correct. Read why.
We have (or are committed to getting) a co-ownership agreement in writing
Before anyone moves in, not after. Eight things it must cover.
We've agreed what happens if one party wants to exit the arrangement
How the property gets valued, who has the right to buy the departing party's share, and what happens if they can't fund it. Exit clause guide.
Both parties' wills are up to date and address the shared property specifically
An outdated will can leave the surviving party co-owning with someone they didn't choose.
The space
Each household has genuinely separate space — not just a room with a door
A separate entrance makes an enormous practical difference to how independent each household feels.
Party B's space would feel like a home to them — not a compromise
If you'd be embarrassed to have friends visit, the space isn't good enough. This matters for quality of life and for the arrangement's longevity.
We've agreed which spaces are shared and the expectations around them
Garden, laundry, parking, storage. Unspoken assumptions about shared spaces are a reliable source of friction.
Any conversion or renovation work is budgeted realistically
Add 20% to whatever quote you've been given. Conversion cost guide.
The relationships
Everyone directly affected has been part of the conversation — including partners
A partner who was presented with a fait accompli rather than consulted is a risk to the arrangement from day one.
We've talked honestly about what proximity will feel like day to day
Not the best-case version. The Tuesday evening when nobody wants to run into anyone. The Sunday morning. The long-term reality.
We've agreed the basic ground rules — noise, visitors, notice before dropping in
Explicit is better than assumed, even if it feels slightly formal. Especially if it feels slightly formal.
There's a way to raise problems without it becoming a big deal
The arrangements that last have a mechanism for small friction to be resolved before it becomes large friction.
Party B would feel like an adult making a choice — not a child who couldn't afford to leave
If the identity question hasn't been resolved, it will resurface. Better to name it than to manage it quietly.
The exit
We have a rough sense of how long the arrangement will last
It doesn't need to be fixed — but "until Party B can buy independently" is more useful than "indefinitely."
We've talked about what success looks like — and what winding it down would look like
The arrangements that end well are the ones where everyone knew what ending well would mean.
What to do with the gaps
Every unchecked item is a conversation to have before you commit, not after. Some will be easy — you hadn't thought about it but can resolve it in ten minutes. Others will take longer, or reveal that one party has assumptions the other doesn't share.
That's not a reason not to proceed. It's the reason to do this now rather than after someone has moved in and the leverage for honest conversation is reduced.
The families who do this well are the ones who treated the setup phase as seriously as the financial decision. The numbers tell you whether it can work. The checklist tells you whether it will.
Ready to run the numbers?
The calculator models your specific situation — monthly savings, equity positions, break-even on conversion costs.