To live together or not..at age 20!

My 20 year old son told me he's ready to live together with his 20 year old girlfriend. He told me, "She's the one!" ---

I consider my son & I to be really close. For the most part I leave him alone and let him lead his life on his own. He left the house at 18 and said he was ready. I was devastated although I kept it to myself. For the past two years he lived with different sets of friends but I saw he is responsible enough to be on his own. Not that there was anything I can do. He's one those guys that he does whatever he sets his mind to do. He's been working fulltime with decent wage and been attending some classes here and there but nothing concrete. He said he doesn't like college and told me upfront not to bother helping him financially by pushing him get a degree. He's an exceptional student back in elementary years and was tested having an IQ of 140+, thus labeled as gifted, which he resented. Highschool was totally different, he barely made it. Not because of lack of intelligence, mind you, but because of his stubborness and strong affinity to breaking rules, or at least trying to.

Now, at 20, seems like he's ready to "settle down" by living together with his High School sweetheart. They were together in their sophomore years and broke up. Now that he found her again, he doesn't want to lose her again.

I am so fond of this girl that I would like her to be my son's wife someday. Yes, someday...but not yet. So I talked to my son about this. Of course, I had to make it appear like it's really not a big deal to me, otherwise, he will not even listen.

My main argument was that, of course, their age. I told him that I thought they're both too young to really take each other seriously. They're not even legal to drink yet. I mentioned my own mistakes for my past relationships, etc, etc.. I enumerated the realities of two people being together and lose respects and eventually lose their love for each other, no matter how much they adore one another - all because of their immaturity and lack of life's experiences...Heck, even older ones, make the same mistakes. I did!

I went on and on and on. Then I said, because I know him, that I really care for his girl that I feel I have to protect her. Whoah! That got his attention. I don't want this girl to get hurt again. My son is very independent, headstrong, adventurous & loves variety. Need I say more? Oh, yes...he's only 20!