As for income requirement, my girlfriend has enough money (12000 Euro or maybe more) for proving. She also owns a house in my country (which I think can be used as a proof that she will definitely come back. As I read somewhere in the Internet that people might need to prove that they will come back to their home countries in order to be granted the residence permit to Finland)
However, my girlfriend cannot apply for the residence permit immediately, she must wait for about 6 months because she is having a contract job now. So for the next 6 months, we won't live together anymore, will it affect the decision upon the residence permit? And this is a really serious relationship, but we are not planning to get marriage soon (at least not until I finish my studies). I also want to ask the possibility for her to be granted a temporary residence permit with all those conditions. I tried to reach the Finland Embassy in my country but they are quite busy and have not responded yet

Are there any other ways to prove that we have been living together? I am trying to find old utilities bills but it's hopeless as it has been already 2 years. And for rental agreement, we don't have such thing because I lived in her house for the last 2 years. I just want to make sure that I have more than enough proofs to prove that we have been living for more than 2 years
I have searched through the forum and found several similar cases
viewtopic.php?f=2&t=74991 which is slightly different because he has a job
viewtopic.php?f=2&t=61374 which is quite the same except that he (or she) doesn't have any proofs
and many other cases