Mother-in-law as tenant in your own apartment

Hello!
We are planning to buy an apartment in Munich where my German mother-in-law could live. She would pay us some rent to cover our mortgage interest, it would be about half of the market rate rent. I read on other topics that supporting your family members abroad has some tax benefits, what would happen in this case? Basically we are doing it because her state pension is very small and at age 74 she is still working to cover living cost.
Or if you know a financial adviser who speak En and could help I would appreciate.
Thank you,
speedy

Much as the locals like to think it is, Bavaria isn't actually abroad (from Berlin)

I have no idea about the tax benefits, but i can't see how buying relatives a house would fit into such a category (could be wrong though)

I am trying to compare the pro/con of sending my mother in law some cash per month as support or buying an apartment which she would rent at a low price. the apt sounds better, however it would tie down a lot of cash and the value might not increase. And who knows mother in law migh live till 100 :-)

Paying only half of the market rate rent, would be a very bad idea in combination with german tax law. If you are getting less than 56% of the market rate rent, you are only allowed to subtract a corresponding fraction of your tax allowable expenses (repair cost, interests, ...). §21(2) EstG

To be sure, I would ask at least 60% of what you consider the market rate rent and better make sure you have some backup ("Mietspiegel") for your estimate.

Also make sure everything looks like a normal business relation. (written contract with normal arrangements, actually transferring the rent on your account monthly, ...)

Since German tax law is so complicated and has so many hidden pitfalls like FREISING already hints to, it might be wise to spend some extra money in advance for professional tax advise. There are some guys advertising here on TT and if you just check a little bit in the comments you'll see who comes with the highest recommendations.

Cheerio

thank you all for the comments, I am searching now TT for a professional tax adviser :-)
cheers