Why it matters
Two things.
How to spot it
A fibreglass one-piece tub-and-surround unit, which has a life of about 20 years and is the default in Canadian homes from roughly 1980 onward; a tub nobody has used in a decade, with a shower curtain still on the rod; a small ensuite where a tub eats the whole room. Count the tubs in the listing photos across all bathrooms before you plan to remove one.
What it costs
We do not have a Canadian source for a standalone tub-to-shower conversion that we are willing to publish, so we will not invent one. What we will tell you is the shape of it: it is priced within a three-piece bathroom refresh if the drain stays where it is, and it steps up by the cost of a fixture move if it does not.
What to do
Monitor. Ask one question: does the drain move? That is the whole cost question. Then ask yourself the resale one: is this the last tub in the house?
Education and triage, not a home inspection. Casaroo can see whether a bathroom has a tub or a shower. Whether the drain can stay put is a plumber's answer, not a photo's. We flag; we don't inspect.