When Shiga toxin is released from an E. coli O157:H7 bacterium, it can translocate to organs other than the digestive tract such as the kidneys and central nervous system (brain and spinal cord). This can cause hemolytic uremic syndrome (HUS) and/or thrombotic thrombocytopenic purpura (TTP) .
A strategy called dollar-cost averaging can help reduce risks surrounding an asset falling in price. The concept is straightforward - you invest a fixed amount of money in an asset once every fixed time period.
The short answer is any profit margin is good! The long answer really depends on long term planning, the size of your business and the markets you are competing in. Long term planning - profits fund business expansion, new product development, new and current market development etc.