Potential 1st deal on quadplex

[Melissa Hall]

My realtor called me about a quadplex that just came up for sale.  Owner sold a few and had one left.  This would be my 1st deal and it would be an out-of-state deal where my son lives.  I had my son go walk around outside the quadplex and a couple that are tenets were outside.  They shared it took landlord almost 3 years to fix central air and he allowed them to put in a window unit (that is still there), they are long term section 8.  
The outside of place has not been kept up when not that old of a place.

I’m not sure if I should go forward with not being able to see inside, has it been neglected like outside?  
Can the other 3 renters still pay with current conditions.

The numbers are very good if all was normal.  Are there big red flags anyone can see?