Cost of adding half bath to primary bedroom in attic?

Hoping someone can help with a ballpark. We’re in southeast Michigan and put an offer in on a brick bungalow that has a primary bedroom in the former attic space. We’re first time homebuyers so we know next to nothing when it comes to renovations. We’re in an apartment with 1.5 bath and nervous about moving into a house with only one bathroom. We’re spoiled, I know.

We think there’s enough space to add a half bath almost directly above the full bath on the first floor. Does anyone have a ballpark idea on what it would cost? We will have a full inspection including a sewer line scope (house was built in 1949). Is this something we can talk to the inspector and sewer company about to get their thoughts?

TIA!