Six rules, and this is all of them.
Per unit, not per portfolio
The average revenue each unit earns per month. Adding or selling units does not move it in either direction.
The same units on both sides
A unit counts once it has a full twelve months behind it, and it is compared only with its own year. The Roomy Share is charged on those same units, so a unit added last month is managed but not charged on.
Rolling twelve months, completed months only
A full year against a full year, billed a month in arrears on revenue actually earned. Never on pace, so a cancellation never has to be unwound.
The bar drops after year one
The biggest gains come first. From month 13 the scale asks for less, and holding a gain you built together earns a share of its own rather than nothing.
No single month can run away
The Roomy Share is charged on up to a set multiple of your average month and nothing above it. Your best August is still your best August, it just stops adding to the fee.
There is a floor and a headroom
A flat year costs you less than the flat price, guaranteed. A year at the top of the scale costs a set amount more, and no more than that.