Until you are willing to marry, I cannot endorse the idea of you sharing ownership of the house. Instead, one of you should own it, and the other should be a tenant who pays rent. You can share the living expenses, such as utilities, but don't buy the television or furniture jointly. (One person should be the sole owner of each item; and document everything, as memories will fade.)
When the relationship ends, the owner can easily evict the tenant with no worries about who-owns-what-share of the house's equity. Conversely, the tenant can walk out anytime, with no financial repercussions or limitations.
If you feel this would never happen because the relationship won't ever end, then get married.
In cases where the partners cannot get married -- gay couples, friends, siblings or parent-child situations -- one should be the owner; the other should invest his/her money elsewhere to be ready for the day when he or she may need to buy his or her own place to live.