Build new or buy an old house?

Very good! Then I hope it works out for you. Do report how it came about.

Buy! When building, you are currently going through hell and back again.

I just took a look at the exposé as well – it’s a no-brainer – very nice house, great interior fittings, neatly paved outdoor area (as far as I can judge), and for the price! Of course, photos of the interior fittings are not initially very meaningful when it comes to the condition of a house; the state of the basement, attic, and technical infrastructure is more important, but these appear – as far as visible – very well maintained. As 11ant already wrote (I hope it was him), I would follow up regarding the one gable wall; it looks damp (which could be due to the orientation of the house, the weather at the time the picture was taken, and the paint used). If you really want to insulate from the outside (which I would consider very carefully), the insufficient roof overhang is not such a problem. A roofer/carpenter can correspondingly enlarge/adjust the roof overhang.

Of course, it always depends on the region, but here in Vorderpfalz, such a house, if it is reasonably well located, would easily cost and sell for twice as much. It would sell quickly.

As 11ant already wrote (I hope it was him), I would, however, follow up regarding the one gable wall, it looks damp (which could be due to the orientation of the house, the weather at the time the photo was taken, and the paint used).

That seems to me to be a ghost shadow, meaning dirt from the air traces where it adhered to condensate. At the time of day the photo was taken, it would have long been dry there. Of course, this practically only affects the moss side. But if it were to require treatment at all, then certainly not at a price point that would justify hesitation. Buy!