Not even close to the 50% rule, why are my calculations so off?

[Chris Collins]

When I've been analyzing deals, I've been getting numbers that are way off the 50% rule.

I know that that's only a guideline, but I'm not even close. Am I doing something wrong? Or am I being too high on my estimations of capex, repairs, insurance etc?

Please advise?? Here's a fourplex example where my Cash On Cash calculates to $43 but the 50% rule would put it more at $670.  Why so far off?!  I feel like an idiot here...

https://www.biggerpockets.com/calculators/shared/3...

50% rule breakdown here:

Total Monthly Income: $2,960.00

x50% for Expenses: $1,480.00

Monthly Payment/Interest Payment: $810.70

Total Monthly Cashflow using 50% Rule: $669.30

thanks in advance!

-Chris