What sort of calculations are used in determining mortgages?

I checked into getting a mortgage, and was told that I qualified for a mortgage of around $140,000 (which where I live is just enough to buy a crack house). With no money down, over forty years, they said my payments would be around $900 every month. I calculated that $900 a month over forty years is almost $400,000. So what gives? What am I missing here?What sort of calculations are used in determining mortgages?
Interest. You're looking at what, 7%? 7% Every year on the value remaining on the loan... 7% of 140,000 (To Start out) is $9,800 of Interest for the 1st year, and You'll be paying a Total of $10,800 on the Loan... The next year you'll be paying Off the Remaining $139,000 (Yes, You see, You only paid $1,000 of the Principal $10,800-$9,800= $1,000) and you'll gradually pay off more of the loan as you approach the later years of the Loan Term. The 2nd Year you'll pay $9,770 in Interest, and $1,030 off of the Principal, leaving you with a $137,970 Loan. See how it works?What sort of calculations are used in determining mortgages?
Yeah, there are no free lunches, Bubba. On the other end, we still are able to write off a lot of that every year for taxes. Then, If the market jumps, your in!!! Take a shot. Just think where you'll be if you Don't! Mike
the interest??