How much should i be making per month on this house? #'s included

[William J Stratton Jr.]

Hey Guys, 

I just purchased a triplex for 127,000 - 30 year mortgage.

I am trying to figure out what i should be making each month off this house? I heard that if you make 10 or 20% of the amount you rent for per month then you are doing well. Can someone tell me if this is true or if there is other ways in which i should be viewing the profit on this house?  

Here are my numbers:

$127,000 purchase price

$30 year mortgage 

Monthly Expenses:

$1010.30 (mortgage payment of 577.50 and property taxes/homeowners insurance of 346.73)

$150 Water (Calculated using yearly amount) 

$215.41 Heat (calculated using yearly amount) 

$20 Garbage 

= $1395.71

Monthly Income:

$700 (Upstairs)

$800 (Downstairs)

Basement has not been rented out yet - needs updating first (maybe $5,000 to $8,000)

= $1500

Thank you all for the help - this is a great community!

William