Is connection to the sewer system mandatory for hobby plots as well?

I am still waiting for a response from the wastewater authority. The remaining information comes from the real estate agent, but I will do some research myself, thank you very much for the hints. According to the real estate agent, who supposedly has already spoken with the wastewater authority, there is only a connection obligation if used as a residential house, but not if used as storage; in that case, only flat-rate charges for the connection possibility might be incurred. I thought until now that a new building permit was only required for the extension of new buildings/higher roofs/etc.? Not for interior finishing? Easement would be contractually arranged with the neighbors, whom I will meet on Monday. That the building is legally standing there is information from the real estate agent, and I thought otherwise only the land could have been advertised. But the house and the land are listed.

Storage is not a holiday apartment.

That is already clear to me, the exact distinction is the question. The wastewater authority has fortunately made contact. As long as we spend a few days working there occasionally in our free time, there is no compulsory connection. Connections run through the neighboring property, so they exist and must be agreed upon with the right of way. If no agreement is reached there, a septic tank is possible upon application. Thank you for the help!