EWH - sell or rent

Hello everyone,
(A mistake has crept into the topic. It is, of course, a condominium - ETW). Unfortunately, I don’t know how to correct this mistake)

We own a 4-room apartment but want to build in 1-2 years.
The value of the ETW is around 300k. About 100k is still left to pay off (mortgage 170k).
What would be wiser?
To sell the apartment and take out a smaller loan or rent it out and use the rental income for the "big loan"? Rental income approx. 750-800€ cold rent. How does it look tax-wise? Could we increase the loan again up to the mortgage (maybe even register a higher mortgage) and deduct the interest for tax purposes? The fixed interest period ends in 2021, so refinancing would fit quite well.
Equity for the new construction project is very low, around 20k, since so far everything has been used to pay off the ETW.
We are both employed, 2 children (no more planned).
Family net income approx. 5000k + child benefit

You can only deduct the interest incurred or accruing for the first loan for the apartment purchase. New mortgage and deducting this interest does not work. You have to consider whether you can afford it if the apartment is not rented out for a while, the tenant does not pay, or repairs are due?

Unfortunately, you absolutely cannot tell from the description. How big should the house be? How big the plot? How expensive should the entire construction be? Basically, I would keep the apartment if I can afford to maintain the house + apartment with my income, but that is my personal feeling. So many criteria come into play... Renting out is also associated with paperwork. At least it should be – there are landlords who unfortunately do not take care of anything.

Sell. For that little return, you have a lot of trouble and risk on your hands with a single rental apartment.

Sell. For that little return, you have a lot of trouble and risk on your hands with a single rental apartment.

Sell. For that little return, you have a lot of trouble and risk on your hands with a single rental apartment.

I thought the same.

You can only deduct the interest that was or is incurred for the first loan for the apartment purchase. New land charges and deducting those interests do not work.

Since when? Purpose of use "equity refinancing" and the tax office is quite peaceful. At least I’ve known it that way for the last 20 years...

You have to consider whether you can afford it if the apartment is not rented for a while, the tenant does not pay, or repairs are needed?

Yep, true. So it depends on the apartment and the location. With a value of €300K, however, I assume that vacancy will not be an issue. Repairs generally only concern the apartment itself and not the common property (facade, hallway, apartment door, windows, etc.)

Sell. For that little return, you get a lot of hassle and risk with a single rental apartment.

Well, the return will be significantly higher than with a fixed deposit. Especially if it is upvalued. Also, not everyone has the cash to buy a portfolio for risk diversification right away. With a good location, a possible price increase should be kept in mind.

Conclusion: Both are possible – keep or sell. It’s a calculation exercise and a question of your risk tolerance and financial background.