allegedly everything is included there, including all ancillary construction costs and the basement. They told the developer a maximum budget of about 300,000 and that they want a move-in ready house with a basement. And he then said he could manage that and said the house would be about 140 sqm plus basement...
Next week he would present a finished offer..
What nonsense :D Ancillary construction costs are never all included
:p
It already starts with the fact that a verification structural engineer MUST ALWAYS be paid directly by the builder - that is just one of many points (but it could also be that this is only the case in BaWü? However, I do not know that).
As a rule, the earthworks are also a construction-side service - here between 15,000 - 35,000€ a lot can happen.
These are just 2 items - 2 of x items.
Either your colleague is talking nonsense because he does not want to tell it or has no idea --- or the developer is simply ripping him off, or is not being "honest" about what ultimately still awaits the builder. Nevertheless, every builder can check for himself which costs will come his way, for that he just has to inform himself sufficiently and study the construction and service description, as I have already mentioned.
If the developer asks only 300,000€ for such a house (of course, those are very sparse details you have there xD) he cannot make any profit from it.