How do you check a construction company?

You speak in riddles, my friend.

Section 34 of the Trade Regulation Act restricts the general right to freely choose a profession insofar as it requires, for example, hospital operators or various financial service providers (including brokers and property developers) to have expertise, personal reliability, and the like. A broker should avoid relevant criminal records (for embezzlement, forgery, fraud, etc.) – for that, he does not need a passenger transport license and may have failed the meat grinder test endlessly. If one has ruined their reputation in a profession requiring a license, one only lives unrestrained if one has a straw man.

And how else does he get these references? Sure, we can drive through current new development areas, but a house that is not yet finished is simply not yet finished.

All the more, there are still tradesmen around who can be asked how often they have already worked for this provider. If they are all "new," their predecessors may have been paid sluggishly...

You speak in riddles, my friend. He basically offers an A6 quattro at the price of a Dacia. About €50,000 cheaper than cheap solid house providers like Team Massivhaus or Heinz von Heiden I obviously can't judge that, since I wasn't part of the conversation. And you can't find any references at all! And how else does he get these references? Sure, we can drive through current new development areas, but a house that is not finished yet is just not finished yet.

Well, most advertise with construction areas. Just drive by and look out for construction signs.