New relationships are exciting, but before moving in together, check out Living Together: A Legal Guide for Unmarried Couples. You may be great at cooking with your special someone, but merging lives is a bit more complicated. While an unsuccessful omelet can be tossed in the trash or fed to the dog, a relationship is harder to dispose of (and you may be more eager to avoid disaster; an egg is $.25, but true love is priceless). If you plan on merging assets, raising children, or writing a will, some legal precautions are in order, and Nolo will give you excellent information.
This book would be handy for relationships other than romantic. Cohabitators of any ilk could benefit from perusing it.
Living together : a legal guide for unmarried couples