Am I analyzing this 4 unit correctly?

[Nick Vehr]

Hi all, 

New as new can be here. I have been starting my research and want to make sure I'm looking at this correctly. It seems too easy, so i have to be missing something. 

Take this for example, assume all things remain constant and its able to continue renting out. I am also assuming all units are rented, and they are getting the posted prices. 

4 unit building asking price is 54,900

Units rent out for 400, 410, 400 and 300 a piece or 1510 combined (we're assuming all are rented in this scenario)

Building is in no need of immediate repairs

Would use a property management company that is 10% of the monthly rent with a 150$ minimum. In this case it would be 151$ a month. 

Would be able to put 25k down on the deal, and taking a 40k loan

Assuming 40k, 5 year loan with 4.5% interest it would be ~745$ a month payments

So if i assume 40% for management, vacancy, repairs (is this number accurate?) I can expect realistically 906$ a month. 

This would put my cash flow on the property at 161$ a month.