Are you asking this strictly as a financial thing? I would think it would be much preferable to live in a house with UC rather than an apartment, unless you are only talking about monthly expenses being a lot cheaper. What's your mortgage like? Are you at a point where you can refinance? I only had 11 years left on my mortgage and recently refinanced it to a 30 year, decreasing the payments considerably. Not only did I get a lower interest rate with lower monthly payments, but I still have the option of making double payments (which would be about the same as my previous mortgage), in which case my house will still be paid off in that same 11 years. I know you are just in the thought process right now but if you are seriously wanting to make a life with your girlfriend and she prefers a home to an apartment, I wouldn't go down that road unless it was financially necessary.
I've actually got my basic bills down to around $800/month, plus a few hundred in things like taking my gf out to eat and such. This is because my home is paid for and I get about
$1,000 every month from some apartments I own.
So... I am theoretically weighing the option of living in my own home and having around $1,100 outgoing every month, or living in an apartment without the need for much earned income. The extra positive about
apartments is that I wouldn't come home seeing all the little things needing done, and feel mentally like I'm always falling behind. It gets to wearing on me.