Barrier-free bungalow, buy or build yourself

Hi guys, I have to turn to you because I simply lack experience and have lost track. I will try to express myself briefly and clearly.

First of all, I am currently in Spain and planning to come back to Germany after the winter. I am urgently looking for a house with a garden (for my big dog, a Labrador) that I want and need to buy. I am a wheelchair user, so I am looking for a house with as few barriers as possible. It would need to have underfloor heating installed or the possibility to retrofit underfloor heating.
Ideally large rooms and few corridors.
From 120m2 is interesting for me. I am currently focusing on searching for bungalows, possibly with a basement. Only my wife, the dog, and I will live there.
The location should be in West Germany, from Münster to Karlsruhe, and from Aachen to Frankfurt.

I am looking for a price of around 500k including additional costs but would have another 50-100k available for renovation or important changes.

It is very difficult for me to find something suitable. I am searching on the biggest online real estate sites.

What would you recommend to me? How would you do it? Maybe a new build would be best if I find a nice plot that already has an approved project, where I can still make one or two changes to the room layout.
Where can I find something like that? And if I do find something like that, is it realistic to realize a 150-200m2 bungalow in a short time, say until May 23?
Can you recommend reliable companies that can build such houses? Is there something like market leaders in this area?

I hope the question is allowed and I am not bothering anyone with it.

Thanks and have a nice evening everyone

New construction will not work.

Land search, planning, company search, approval, construction.
Building alone takes at least 6 months, the rule is rather 12 months until ready to move in.

Either buy a project under construction that suits you.

Or look in the existing stock, or in the narrow niche: have a realtor search for you. Even just because of the distance, this is a sensible thing. Check out the bigger realtors, you have a large radius. Or see if there aren’t even realtor experts for people with disabilities.

Small side question: I have in mind that dogs do not tolerate underfloor heating well? Of course, this may be unproblematic for your dog accustomed to Spain?

Thank you for your answer.

Yes, I already thought that completing the entire new construction within the timeframe would not be possible. That’s why my idea is to acquire a project that’s already approved and only waiting for an investor. I have also tried consulting a real estate agent a few times, but after the initial conversation, I never heard from them again. Could you recommend a large real estate agency? Honestly, I had never considered the underfloor heating and dog issue before, so I’ll look into that, thank you.

a 150-200m2 bungalow

and

approx. 500k incl. additional costs, but would still have 50-100k

could already conflict. If you roughly assume 3000 euros / sqm without land costs. The tendency is rather towards 3500 euros/sqm.

Up to 500000 and house construction is not happening. Not even planned.

That's why my idea is to acquire an already approved project that is just waiting for an investor.

Planned properties are usually associated with effective house construction and space utilization -> terraced or semi-detached houses, rarely bungalows, rarely niche coverage.
For several years now, the market in Germany has been practically cleared out, and exorbitant prices are still being demanded.

Immowelt 2693s5f, 26ch656, 26yz75s

Just quickly, in the middle of the search area (50km around Koblenz).

There are still cheap areas in Germany ;-)