MV, ok, thank you for clarifying. Yes, I get the same answer with the same assumptions you are using. Note that the return on investment would be typically calculated as the total return divided by the initial investment ($169k / $320k down payment) = 53%, but since you are adding money every month your way of thinking is also appropriate.
Also, that is the total return on inestment, not the annual rate of return. To get the annual rate of return, you would want to use a time value of money (TVM) calculator such as http://www.fncalculator.com or Excel to use the FV formula to solve for "rate". I get about a 0.7% annual rate of return (compared to say a historical 10% return in the S&P 500 index).
PV = -$320,000
PMT = -$92,000
FV = $2,325,307
Periods = 20
rate = 0.66%
And to get a more realistic number, you would want to include all the expenses that were left out. The return would go negative.
Hope that helps, thanks!