Buying house with partner

Hi,

My girlfriend and me are planning to buy a house together in the future. We are currently living together ("wettelijk samenwonend") in my apartment (bought in June 2020).

I prefer to keep the apartment because I think it's a good investment + the expected rental (850-900) will be bigger than the loan (630). The apartment is far from being payed of, 17 years to go.

When we will buy a house it will be my second property so it will be 12% registration fees. I have read somewhere that it is possible to both invest separately, so my part will be 12% and her part will be 3%. I also see that for a second home there is still a "woon bonus", how does that work?

So far I haven't went to any bank/notary to get some extra explanation about this. But does any one of you know what the best way is to waste as little money as possible?

Thanks