Am I missing something on this $700,000 Property?

[Manuel Scott]

Hey guys,

I'm about to put a 20-unit property under contract, and would appreciate your insight.

The property consists of 20 units, fully rented in a C area. 15 people on waiting list. I viewed the property with the manager, and the units are nice. Most units bring in $400/mo; the few that have been renovated are pulling in $600/mo. So there appears to be a nice value-add opportunity here. 

Asking, $750k, but appraised at $650k.

Income: $9,500/mo

Expenses: $2,900/mo (insurance, taxes, maintenance, property manager, etc)

Debt service: $2800/mo (20% down, 4% interest-rate, 30 yr)

Cash Flow: $3,800/mo

It's been operated like a mom-n-pop property, so we don't have rent rolls yet, but from what I have listed above, the numbers seem to work, even at asking.  

This will have been our biggest investment so far (we have a quad and a couple SFR), but want to avoid any blunders. Please help.

Manny