Construction of a bungalow in the garden

I plan to build a bungalow in our spacious garden. This is intended to be rented out later as a holiday apartment or as living space for craftsmen. First, I would like to determine how high the costs will be and what the best approach is for this. Does it make sense to hire an architect for this, go directly to a construction company, or maybe buy ready-made plans and implement them with the corresponding craftsmen? I would be very happy to receive any tips or experiences.

EBK is currently building an entire bungalow settlement here for rent to holiday guests. About 50 units. They have what you are looking for. Karsten

However, it must first be checked whether the garden is even buildable. Many factors could speak against it - the development plan would have to allow for a second unit, floor area ratio, and building envelope.

Regards, Yvonne