For us, the connection was only included in the flat rate. Every meter in unpaved ground around 80, in paved ground 100 EUR net. With you, it could easily be 25m, so for electricity and drinking water about 5,000 EUR gross, possibly more if the line is on the other side of the street. You pay up to the main cable, not up to the property boundary ;)
Definitely plan, mark, and be present during installation for the technology in the HAR. We also painted everything nicely on the rough wall with installers and site managers, in 3 different colors. Then came the plaster, I was under the illusion that the craftsmen had the plan from the inspection with them and suddenly...
The heating circuit distributor is where the washing machine was supposed to go, the pipes to the bathroom run right in the middle of the wall where a shelf was supposed to be, the house connection box is not where it should be. Only Telekom screwed themselves in where it was planned. I was there for that, I had to let them in...