Very good questions you have posed and I appreciate your courage in approaching this forum for the answers! One question for you – independently of this offer, would you have needed/wanted 3000 square feet for your family of four? In other words, would you have been looking for this size house if your friend had not approached you?
It might be a good deal for the price, but too much house in other respects. When you do your calculations, consider the cost of heating/cooling/furnishing a house of that size. I think some people are getting away from bigger homes and graviating towards smaller since they are easier and less expensive to manage.
I know a couple of people who live in 4000 – 5000 sq foot homes who regret having that much empty space – yours isn’t that big but I thought I would bring this up.
My personal experience was, I bought a house with a 10,000 square foot lot and had visions of water features, grottoes, tropical gardens, and whatnot dancing in my head. It only took a few months for me to curse the lawns and terraces and I eventually sold the house because the foliage was just too much to handle and maintenance was more than I had originally considered.