Oh, okay, so you've only been together a few months but won't be moving in until you're almost at a year? Okay, that sounds more sensible.
I will defer to others who cohabit with their partners to offer advice on what to look out for and how to prepare, since I live alone and have no desire to live with anyone.
There is a big thread here on living with multiple partners, which was started by member MonoVCPHG, who would also be a good person to ask for input. Here's the link: Multi-partner co-habitation