the only time you should ever do a deal with a nigerian is when its cash and then get the cash tested afterwards. One of their traditions is called Dashing, in english it means a bribe or backhander. L lived and worked in lagos and we were not allowed out of the compound without a guide and he made us take all jewerlly off and leave our money in the safe.
even then you only need to upset the wrong nigerian and then you do a short time in kri kri until you pay the fine, so don't trust them at all.