Registering a business for self-builders - sensible?

What is the supposed advantage?

Chamber fees
GEZ
Business liability insurance
Annual financial statement
Trade tax
Value added tax
Income tax
Registration for mandatory wage and social security contributions for all construction helpers
Wages above minimum wage
Etc.

And then the tax office determines it to be a hobby activity

I once heard that it makes sense to register a business for self-construction.

I have to chuckle a bit. I know this from the 70s from a satire. It might be time again to recommend the film to our building-aspiring Netflix viewers.
Once in a Life - The Story of a Home
Is available as 2 purchase DVDs

The couple goes through all the clichés, every blunder, but also the business registration so they can buy the cladding and tiles themselves. So it might be that Grandpa gave you the tip.

I don’t believe that a sole proprietor has advantages in trading. Advantages are networks, and those don’t exist on paper. I wouldn’t dismiss the mentioned obligations so easily either.

P.S. I took a look at your other questions. It reads like you are taking on too much yourself right now: spending money without expertise.

What is supposed to be the advantage?

Example:
The house belongs to the established company.
Tax advantages arise when selling the company (with the corresponding profit). Instead of income tax on the profit of up to 45%, only 25% capital gains tax is charged. You can sell at a higher price because the buyer of the company does not have to pay property tax. After all, the company changes ownership while the house and land keep the owner, namely the company.

There would be many more examples. Unfortunately, this is only for professionals with substantial capital. As the saying goes: The devil always sh*ts on the biggest pile. Most of us are rather busy making the pile ourselves.

You found a GmbH to pay only 25% tax which would not be due otherwise.

The TE wants to build his house with a lot of own labor.

Helpers without a business tax, tax- and social security-free, far below minimum wage as unpaid

Sale after 10 years tax-free
(As long as he does not sell other properties during that time)

You asked for a reason. The OP once heard something. Therefore, I gave a common example. I also suspect that it is not relevant for the OP.

Hello,

buying cheaper as a company. I could imagine that.
All those who have written do not know about this matter.

Thanks anyway for now.

Regards, Alex