Good deal or bad? Feedback appreciated.

[Paul Ho]

Alrighty so.. still looking to do my first purchase.

Duplex each unit 4BR 2BA. Built in 2002. 

Listing price: $99,900

Currently rented with tenants paying $750 & $800 per month.

Using 50% rule: $1150/2 = $575

By choosing a 30yr mortgage - 10% down - 4.1% int

$575 - $435

= $140 CF

now this is without having to throw any offers yet as I am still in need of a agent.

How do the numbers look? 

Still a newbie here so I probably missed something

-Thanks :)