Found a very rare deal on a house...

I can't believe what happened to me the other day. Me and two friends go looking around at big homes here in my city. One of my friends is a realtor so he lets us all in to look at them. The first one we look at seems just amazing. And initially in doing some quick math I thought they would be leaving about $200k on the table. Then we looked at it later that day again and I just was sold. So I put in a list offer at $640k that was accepted the very next day. But here's the kicker...There's houses all around this one that are about the same size most of which are worth over 1m. One of those is listed. It's about the same size as mine is and it's listed at: 1.3m. I have a feeling as though there is a chance that they have left as much as $500k or even more on the table on this deal. However, even though it would be a good flip, I'm just gonna keep it rather and live in it.