Numbers for a 2 family rental.

BP gang,

So, we haven't been able to secure a flip but have seen some OK rental deals. I'm currently looking at a 2 family in a decent part of the neighborhood in Amsterdam NY. 

I see the breakdown like this:

55K purchase price

Taxes, Ins. Mort. , 90% Occ rate, -10% for repairs = approx $11,160 in annual expenses

2 tenants $650 +750= $1400 mo /  $16800 annual income for a difference of +$5640

Water, sewer, garbage all included in taxes.

Renters pay utilities.

As I understand the "cap rate" NAI/PP(-mort) = 0.11

Considering overall property conditions, inspections etc. the numbers seem to work , right?

Thanks for your info in advance!

Jason