I may be an exception but I have done this. I’ve had my guy for 21 years now, but we have never married.
We don’t have to marry formally since we live in a state that recognizes common law marriage. We are not religious and don’t care about a church service (which is not a legal marriage) and the common law rules already describe us as married so there is no reason to go downtown to fill out any paperwork.
If I were your friend in her situation, I would be a little more cautious. For one thing, I think it takes more than a year to really get to know someone and see how they handle themselves in a variety of situations. A second thing is that they have not lived together: I would do this before plunking down some big money and making some big financial commitments together.
If you are opposed to their plan, you might suggest to her the sensible plan that they live together in a rental and save some cash before house buying. That will allow them to give it a try before all that paperwork.
If my guy and I separate, we are supposed to go through formal, legal, divorce proceedings. Given our history of not doing stuff like that, we probably would not do that either.
Our kids are nearly grown. We’ve had the house for 15 years, but dated and lived together during the previous 5-6 years so knew each other pretty well.
The only thing we did that was unusual was that I made a rather large down payment and he made all the notes for the next 5 years to equalize our investment in the place. One we were ‘about equal’ we share the bills and are both comfortable with the fact that if we did separate, it would be fair to sell and split.
All of this only works because we are like-minded on these issues. If we were not, of course we would have to go the legal route to sort it all out. Sometimes even like-minded folks get angry and vindictive during divorce, so there is always a chance of that. I still think it would be unlikely in our particular situation.
I can’t speak to the ‘adultery’ angle. I don’t think that plays a large role in my state, but I could be wrong. I guess the importance of that issue depends on the attitudes of all the various and assorted ex’s.