What should be particularly considered regarding the construction ground - soil?

Hello We are interested in a fully developed building plot for sale from a private owner in the town. Now the access road to the property itself is about 30 meters long (6 meters wide). After the 30 meters of access road, there is the actual square building area. Now it is the case that the supply lines must be laid from the access road to the property, which is somewhat more expensive than if the main road were only 5 meters away. Therefore, our question is what one should inquire about and research in order to roughly plan for the ancillary building costs so that one does not experience an unpleasant surprise later. It is clear that for water and wastewater a small trench must be dug on the construction side for the meters from the street to the house... (In the family, we have a mini excavator with which we can take care of this, provided no rocks or similar turn up.) So far, we have called the energy supplier and learned that a power line runs from the access road across the property and can be "tapped" there, so only about 5 meters need to be dug to the house. At 30 euros per running meter, this is negligible. The bigger concern is actually whether we can dig deep enough for the supply trench. The owner cannot say what the soil condition is like... Should one get a soil survey beforehand? Or dig a few small holes with a spade to see if one can reach the minimum depth of 1.20 meters? The house itself is to be built on a slab foundation and the plot is almost level. Only minimal slope at the outer edges, where the house should not even be located. It would not be good to have enormous costs because shortly after the turf there are lots of rocks. Should one think of anything else besides electricity, water, wastewater, telephone for the sewer work? Thanks for tips.

A soil survey is advisable - before the purchase, whereby at least in our case the drillings were carried out at various points on the area where the foundation slab is to be constructed (costs around 1000€).

For the long driveway, check with all suppliers how many meters of cable are included in the connection flat rate. Often it is 15m, after that additional charges apply. The trench is the smallest item, credits for trenching done by oneself are rather low. A larger item is likely the wastewater line from the house to the street, especially if it is not straight but has a "bend," then additional inspection chambers may be necessary.