Robert welcome to BP! Multi families in Bergen county inventory wise is low and the right property does sell fast so i suggest that you are always on the lookout and ready to move quick.
For example a i have an investor client who we searched for the right property for about 9 months but once we did find it now he is generating $2,000 positive cash flow each month which is amazing.
Some areas i can suggest are mostly southern Bergen County easy for commute like Lyndhurst, North Arlington, Rutherford, East Rutherford, Carlstadt, Wood Ridge, Hasbrouck Heights, Lodi, Garfield, Hackensack, Little Ferry and Cliffside Park.
These are some areas you can find somewhat affordable multi families that will give you a positive cash flow. But things you should consider are proximity to transportation, do you want a move in ready or fixer upper (big difference in prices), do you need to get pre approved, does property have attic or basement you can convert, does house have user friendly layout, can you change layout for maximum use of space, how is parking on and off the street etc.
If you dont have one, find an investor friendly agent who knows the areas you're targeting and scan it daily for deals and to walk you through and hopefully an early retirement can be on the horizon!