What are some resources when determining price for duplex?

[Derrek J Hooyman]

I'm putting my first offer in for a duplex that needs some work.  It is what I'm looking for but I don't wanna lose money.  I know what the rent is but think it will be competitive.  Any advice on determining the price for the offer?  I thought Bigger Pocket had some resources.  I'm new to owning a duplex and will need some assistance to not lose money.