And don't buy a house with a girlfriend unless you REALLY plan on staying with that girlfriend or turn her into a wife that won't divorce you...
Don't buy a house without having an independent inspection done.
Some newer homes built in nice subdivisions are actually VERY shitty houses...nice at first, then everything starts breaking around you...So if you are not a very handy guy or make shittons of money, plan on it sucking the life out of you...
Get a warranty on the home if you can to cover the big ticket items just in case...
One of the easiest ways to look for quality well done construction is to see how sound proof the rooms are...so have your girlfriend go into a bedroom...shut the door...and walk to another room and try and have a conversation...if you can, the materials are thin, the walls are thin...if the sound is muffled pretty well the home structure itself is probably pretty well made.
Another thing to look at is the ground that the house is built on...is it soft? Is it rock? How thick is the slab? How thick are the basement walls? Any cracking in the foundation? As a house settles things start warping and bending making it harder to shut windows/doors and can cause other issues with seals around the house making it cost much more to heat or air condition it.
There are tons of things to look at when buying a house...the biggest thing I can suggest is make sure you can afford the cost of maintaining it. Be sure you can afford the heating or cooling costs of the home, especially if fuel used spikes in price(can you afford $3000 in heating oil over a 5 month span?) Just some suggestions to look at