Rental income in
Germany will be covered by limited
tax liability. But owning real estate will trigger extended limited tax liability. It means that especially certain kinds of passive income like stock market
investments that otherwise wouldn’t be taxable in Germany, will remain taxable in Germany for ten years, or something. I would also assume that you will have to submit German tax returns for at least those ten years. I would think that if you gift the real estate to someone else, you can avoid the matter. Other rules that can trigger that is being a partner in a German company and a couple other thing. But I’m no expert on the matter. Please consult with an accountant or tax lawyer.
Yes, if you can prove that you spend more than 182 days in Malta, I can’t imagine anyone being able to dispute your Maltese
tax residency. You could probably be gone more than that, too, but it wouldn’t be as clear.
You have to read the DTA signed by Germany and Malta (or ask a professional to do it for you) and read about the details, especially how taxes are split (exemption method vs. credit method). Typical risks would be that by keeping an abode in Germany (doesn’t have to owned by you, you don’t have to spend much time there, but it is available to you, you have a key and maybe keep some of your stuff there), you would remain German tax resident by domestic law. The DTA would move the tax residency to Malta because you spend more time there, but depending on the DTA, Germany could still tax your worldwide income and only give you credit for taxes paid elsewhere. I believe they do that with Switzerland and the UAE, for example. Countries like Germany have a lot of such rules to screw you over.
As you can see, this stuff is complex, and it would be complete madness to do it without assistance from a professional. I’m not talking consulting for thousands of euros, but a few hours with a professional going through all your affairs and explaining potential pitfalls. There are many tax lawyers and accountants who are specialized in helping people move abroad. Good luck.