What important facts should I know before engaging in buying Sunflower Oil From Foreign countries.?

I have a customer overseas that is looking for 1000MT of Sunflower Oil refined, to be delivered to Mersin, Turkey. I see a lot of so called companies/ brokers offering me their pricing and products. The pricing I'm getting has fluctuated from $200-300US/MT to $1350US/MT. This has raised a RED FLAG for me. Can anyone tell me what important facts do I need to know before engaging with any company. I know there are a lot of companies who are frauds and place adds to entice you to do business with them, I don't want to fall into a trap. My customer trusts me but I am a lot more skeptical than he is in doing business with companies overseas that I never done business with. I just want to know how can I be sure (is there a way) to investigate a company overseas to ensure proper transaction? I see terms like ICPO and Payment upfront and that put shivers down my spine. Can anyone help me please. Ali