Other Reasons to live in Germany
You are saying that there are also other reasons why a person could live in Germany. Which are they?
The statute has something like a "catchall" provision in §7 I 3 AufenthG, reading: "In justified cases, a residence permit may be granted in cases not included in this statute." Of course that is nothing but legalese. However, the Federal Ministry of the Interior is dreaming of a rich foreigner that just wants to live in Germany and spend his fortune here. However nice that dream may be, there is a practical importance to this. It will cover unexpected cases. Do not forget, if a more specific permit / reason seems possible this will block any application of this permit.
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Goodie, I don't have a job so I will claim to be rich and come in with these grounds. Will that work?
No! The law maker is not really dimwitted. Claiming to have a fortune is not enough. You have to show it! You still have to meet the general prerequisites to be allowed to live in Germany. The officer will weigh your interests, as described in your application, with public interests. In doubt, this approach will be denied. However, maybe you qualify for the permit "Job Search". Please click and take a look.
At home, I am considered to be very rich but when I look at the rate of the Euro I get dizzy.
To be very straight forward, German authorities are not interested if you are wealthy, poor, or homeless in your home country. You have to be rich according to German standards. In Germany, being "rich" would start with a higher five digit monthly passive income - in Euros. Passiv means not achieved by work or business.
Could give a few examples?
A foreigner owning a vacation apartment and wanting to often use it, wealthy pensioners wanting to live near their adult children. Bear in your mind, this reason may not be used when other reasons have failed!
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What about my poor elderly parents, can they follow me as "family reunion", too? I own a big house and have enough income to support them.
Yes, this will be another example for "other" reasons. Since they are financially not so well off then you will have to be able to sustain them, – i.e. on top of the needs for your own family. Keep in mind that the office will check all requirements with great scrutiny.