Attic conversion with a 25-degree hip roof - a sensible project?

The least conversion costs occur if you simply install a folding bed in the very large office.

A very good suggestion, thank you. The garage is currently unheated and has a typical garage floor covering (concrete and then sealed?). Does a utility room with washing machine & co. have to be heated?

The room should already be frost-free if water pipes lead there.

The room should definitely be frost-free if water pipes run there.

Is an unheated garage frost-free? And if not, is it easy to lay a pipe there? Drywall and insulation are then clear. The heating is also directly in the next room, so basically not a long distance.

Is an unheated garage frost-free?

As far as I know, no.

And if not, is it easy to lay a pipe there?

Probably, if the heating is sufficiently dimensioned.

There has never been frost in my garage. My water and beer bottles have always survived that. In case of emergency, just put in an electric heater and that's that. You can also leave the door to the [HAR] open.

With 1400 sqm, one could also extend. Perhaps that is more feasible with 70k than the attic conversion.