[jankor]

The regulation gives absolutely insane incentives. In my case (old contract in hip mitte area), it was easier to keep it and for my gf to rent another apartment on the outskirt where her work is as she can deduct the full rent from tax. Effective price for renting two apartments is lower than one in between the center and suburb.

[ascar]

I don't see how that has anything to do with the rent control regulation? What would your expectation be without that regulation?

Doppelte Haushaltsführung is a tax relief for people needing a 2nd place close to work. Also the work of your gf needs to be at least 1 hour away from the main apartment [1], she has to pay at least 10% of the cost of the main apartment to be allowed to deduct it (and maybe more requirements that I'm forgetting right now). She also has to pay 15% additional Zweitwohnungssteuer on the rent of the 2nd apartment.

[1] https://www.haufe.de/personal/entgelt/verwaltungsregeln-zur-...