Is buying a house for a maximum of €350,000 realistic?

Q2 is sufficient for wallpapering. Pure painting will probably annoy you as long as it is more than the [HAR] and you have installed your lamps in the end.

Q2 is enough for wallpapering.

But that's only enough for the good old woodchip wallpaper... Forget about wallpapering with painter's fleece.

I would also take at least Q3.

I would also take at least Q3.

I will take a look at it. If necessary, I will let a few colleagues (I am Polish myself) come from Poland and they will handle it.

Without filling and sanding presumably? How many m2?

Yes, with filling and sanding, but of course it does not go up to Q3. It is only prepared so that you can wallpaper properly.
So rather repairing smaller defects at Q2. I don’t know exactly the m2, we have 152m² of living space.

Since we are on the topic. We would build ready to move in with interior plaster of quality Q2. Does it still need rework or is it enough to just paint over it?

We also got Q2, and according to the painter even good quality for Q2 plaster. In the utility room we leave it as is, but for the living rooms it would be too rough for me personally. The house will still settle in the coming years, and if you only paint you will see every tiny crack. With wallpaper you might be lucky and not see everything immediately.

That is only enough for the good old woodchip wallpaper... Forget about wallpapering with paintable fleece.

Our painter wallpapers "Vliesfaser" from Erfurt. It is not quite as thin and somewhat textured. I would definitely not use very thin paintable fleece. You can try it out at home, take a sample of a thin paintable fleece and put a grain of rice on a smooth table. Then see how big the grain of rice is, and then firmly place the fleece on top. The bump looks much bigger than the grain of rice was before. That’s kind of how thin wallpapers behave on not quite smooth walls. At least that’s how my construction manager explained it to me, sounds plausible to me.

Topic KfW... we have received a rough cost estimate from a regional structural engineering company after having a very positive conversation.

Now my question ... does it have to be KfW 40? We have to install a photovoltaic system anyway (requirement of the development plan). The extra cost for KfW 40 would be €23,000 here. Financially, that wouldn't really be worthwhile, or am I missing something?