Who is looking, and what does each of you need?
Add each person and what they actually require. Nothing is matched until you run it, and a flat only qualifies if it satisfies everyone’s non-negotiables.
In so far
How the rent is split, and why it is checked per person
Rent is divided equally, then each share is checked against that person’s own ceiling. A flat is affordable only when it is affordable for everyone independently.
Adding the budgets together and comparing the total to the rent would pass flats that quietly overcommit whoever has the smallest budget. Under an equal split, the tightest ceiling in the group sets the rent limit for all three — worth knowing out loud rather than discovering in month two.
Traffic
Journeys are checked at weekday office hours by default, because that is when the commute that matters actually happens.
Their requirements
Answer for what they actually need, not what you think they should want.