seller sells for  1,000,000 .  cost 700.000, depreciation 200,000-

he has mortgage of 900,000, --All he buys is one property for 100,000 as exchange.  I get taxable gain of 500,000

He got 100,000 cash on sale and put this 100,000 down to buy new property, all cash. 

lacerate calculates no taxable gain. where I am inputting incorrectly?