Small apartment building. Good buy?

[Thomas Brady]

Hey Everyone, 

I have been working with an investor trying to find a good rental property to go in on and I think I might have found a diamond in the rough.

Here it is: 

Asking $582,000

12 unit 3/2 apartment building

All units rent at 900/month so $10,800 monthly or $129,600 gross yearly profit 

20% ($116,400) down at 4.1% over 30 years = $2,250 mortgage per month 

50% rule deducts $5,400 

Total costs: $7,650/month which leaves $3150 net profit per month or $37,800/year 

COC return: $37,800/$116,400 = 32.47%

These numbers look very strong to me, but once again I would like the eyes of seasoned investors to look them over an see if there is anything I missed. 

FYI: I rant the numbers using a 70% rule and it still came out in the black. 

Thoughts????