Should I do this deal?

[Natalie Kondratenko]

My realtor/property manager has a listing for a 4plex in a low-income area and has talked to the seller(s)...4 partners, about the idea of providing a second for the down payment. The bank I use will allow a second. Here is the terms of the deal:
100k purchase price
20k second at 6% amortized over 20yrs with the final balloon payment after 3 yrs.
Renal income is 1600 a month and the units are 2 bed room 2 bath 1000 sq ft apts.
Market rent is between 400 - 500 per unit in the area. My manager has 15 fourplexes that he manages in the subdivision out of about 60 blogs.

I'm concerned about the fact that it is a low income area with the usual problems - drugs, petty theft, domestic violence, etc but I don't feel uncomfortable when I go there and my manager says he is not uncomfortable day or night. There is a strong police presence there to keep the crime at bay.

The roof is about 7 years old, relatively new ac units in 3 of the units, 2 long term tenants, the other two within the past year. The building has been well maintained and the exterior was recently painted.

What else should I consider to make my decision?