Planning Renovation / Refurbishment of 20-year-old House

For example, I would paint/varnish frames and doors...

But he wants it to look nice. ;) And if he has to bring in a professional for that, I would also say "One time new, please".

As already mentioned here, these are primarily normal tasks that are carried out during every move-in, except for the heating issue.
If underfloor heating, then completely and directly WP.
But that really has to be planned.

COP 3 with the heat pump can already be achieved with renovated radiators. For a house from 2002 with mainly underfloor heating, it is easily achieved. Just for the cost estimation.