This is an important and difficult question for any young man, and there is plenty of sound advice here. I am 60, and perhaps not in the best position to offer a comprehensive answer because I never had a family, and it's always said the expenses of a family are difficult to anticipate.
With that said, I'd like to offer a few points. First, unbridled acquisativeness is a losing proposition. You are never satisfied. You are far better off if you can be satisfied with a modest life. For example, for more than twenty years, I have lived in a one bedroom condo. It suits my needs and I've been quite happy here. I know several guys in my position -- older, no family-- who have large expensive houses. I admit I could not afford that way of life, but I have no desire to live in a large empty house. Second, as others have pointed out, you will want to have enough money to meet your needs with some left over for charities. I've seen guys worried day to day about paying bills and it's enervating. Third, save for retirement and start young. I started saving in my twenties, and it really grows over a thirty year period.
I also have a thought for the young guy who says he doubts he will ever get married because the responsibility is "terrifying." I think this is a normal way for a young guy to feel when he thinks of marriage in the abstract; that is, without respect to any particular woman. I was married for several years in my twenties.I think that for many young men, the prospect of marrying is terrifying until they get to know one particular woman, and they begin to see that being with her for life will be a sorce of great comfort, companionship, etc. That's when the fear subsides and getting married seems like a natural, desirable thing to do. I wish both young men a bright and happy future.