Once I get married, my girlfriend and I probably won't be able to live together until we find a flat. Would that be a problem with the legal process?
Yes, because you would obtain temporary permit to stay in Poland on base of marriage. Border guards make unannounced controls, weather you live together. When not, then you can be accused of fake marriage.
From wedding to citizenship runs long and winding path . First foreigner can obtain a residence permit for a fixed period - and then , when the " circumstance which is the basis for applying for this permit justifies his residence on Polish territory for a period longer than three months ." As emphasized , however, Ewa Piechota, a foreigner poślubionemu Polish citizen is much easier . This does not necessarily include demonstrate that it has a "stable and regular source of income " or health insurance "is not required to also provide the legal title to the premises occupied ." And as a foreigner before hiding as an illegal immigrant , you can not deny him a residence permit (if the illegal stay in Poland would be the basis for the refusal).
It is , however, the Act on Foreigners record , on which fictional spouses curse violently . " The authority conducting the proceedings for granting a residence permit for the duration of an alien who is the spouse of a Polish citizen shall determine whether the marriage has not been included in order to circumvent the foreigner provisions on granting authorization ( ... ) ," says Ewa Piechota the submitted documents. - It is very difficult to prove. Registry Office may refuse to grant a marriage , even if it has any suspicion that it is concluded convenience - explains Col. Pilaszkiewicz.So perhaps get married only when you will be able to live together. No need to hurry.
Btw. Have you asked through the websites which told you? Are they answering?
