Always be cautious and evaluate couple of things

1. CAP rate
2. cash on cash return
3. if there is deferred maintenance, what's the cost
4. factor in rising utility cost if you cover common area
5. check with city if there is special assessment due
6. get insurance quote from your own agent
7. if tenant gets a rent break for providing certain service, e.g. remove garbage

If you suspect the rent income and expense, it's a good idea to ask seller for last year's schedule E that shows his tax filing for subject property. It will tell a true story.