It is possible to obtain a residence permit on the basis of one’s own assets, which can also consist of real estate, pursuant to section 7 (1) sentence 3 of the Residence Act.
According to paragraph (2), unmarried children of minor age, spouses or partners who live in a domestic community with the holder of a residence permit under section 107c (1) of the Residence Act may also apply for such a residence permit
The Ausländerbehörde can give you a Fiktionsbescheinigung if your old residence permit expires soon, and your new residence permit is not yet approved.