Asking neighbors never hurts and can give a general idea. Still, the soil is always a huge lottery and can range from being lucky to ending up in a court case against the seller. Both have happened within 50 meters in our new development area. Some didn’t even need the usual 30cm excavation, which is typically included in the BU price. Others had to have the entire! property replaced over 2 meters deep because they found not-so-great things in it (which then led to a lawsuit). Our neighbor with the house 10 meters from ours had a building expert report done. Since he built with the same company as we did, they simply used his report for our property. It was sufficient for the house; with rainwater drainage, the big luck came. We had high groundwater and therefore about €3000-4000 in additional costs. A prior report would have saved at most €1000 of the extra costs, so we played the lottery, lost but in the end didn’t pay more than expected. So: ask your immediate potential neighbors. That way, you also get to know them and certainly receive great tips for planning, etc. With €20,000 you can already get quite far with earthworks. Probably on flat terrain, even with bad soil, half of that will suffice. If you can somehow do the earthworks yourself (agriculture with a tractor + trailer and transporting the soil to the farm or something similar – even 500 sqm just disappears like that...), the costs are a joke anyway (only the material for backfilling costs).