Sharing static IP address over a WiFi

Hello everyone! I use a static IP address and I have set up a small type of server to track my small business. As I am running business from my home, I am having two network lines providing Internet. Those are business and residential lines. I am thinking of getting rid of the residential line because it really is useless to have to lines at the same time. I think that business line can be used for the entire house as well. But someone told me this could be dangerous. Is it really dangerous to share a WiFi network by using a static IP address? Is it safe or not? Help!
