“Average to good” is too broad to assess likely maintenance. It would help to have condition notes separated by roof/exterior, heating, windows, plumbing and interior finishes, without assuming all of those need work. The energy-performance information may also indicate which questions deserve...
The main difference is not simply maintenance cost but how much of it you control. With the serviced apartment, inspect the management agreement, recurring charges, reserve position and limits on your ability to change operator or use. For the mixed-use building, budget for uneven capital works...
Property tax may not be the cost that hurts most. With a villa, repairs can be irregular and concentrated: heating, roof, exterior, drainage and services can turn a good average year into a bad one. A single generic reserve is only useful if it reflects the likely timing and scale of those jobs...
The gross-yield arithmetic works, but the missing fact is what the €4,874 actually represents. Is it pure rent, or does the figure include charges that are collected and then paid onward? I would obtain the unit and building expense histories, insurance figure, energy information and details of...
The difficult part is keeping the payment affordable if the move does not happen when expected. A quote that looks cheapest over five years could be poor value if you remain in the Berlin property for fifteen and face different exit costs.
I would ask for written illustrations at several dates...