Soil survey before purchasing property?

So if you can manage the purchase of a plot of land in the Cologne city area without external capital, then I would first secure the plot of land. With the equity ratio, you will also get money for the construction.

Personally, I no longer see the issue of [Altlasten] so dramatically at first, since the plot seems to be located right in a developed residential area. Or have all the previous owners suddenly died of unexplained diseases? With such an old property in the middle of a residential area, I am more relaxed than in a mixed-use or commercial area or former "[Kuhlen]" ([Tagebau]).

By the way, you will not simply be allowed to fell THIS tree, see the tree ordinance of the city of Cologne.

The general contractor and also any other provider (prefabricated house manufacturer), etc. will not be able to present you with a serious offer ad hoc. Unless you already have the final house design with detailed planning for execution and interior fittings in the drawer, which also complies with the building authority’s requirements. Therefore, if you cannot wait forever and it is your dream plot, clarify open questions such as building encumbrances and possibly fears of [Altlasten] and buy.

What kind of tree is this? Conifer? American?

I also see the mentioned felling problem. First identify the type and check the possibility of felling, then check the felling time. From spring onwards, this is usually forbidden.

The property is not located in Cologne (here I gave up trying to find something affordable that is bigger than a shoebox) but in Frechen-Königsdorf. I do not want to cut down the tree at all, but absolutely want to keep it. However, I was afraid regarding the roots that there might be heavy restrictions or problems during and after construction. It is a wonderful tree and for me it defines the character of the property. I currently do not know what type it is.