Yes it can be exhausting but you have profits coming from the different business you are running, you can not compare it to someone that is just running one business and is only making profit from that one business, then a serial entrepreneur who has multiple business under one company. I don't agree with your last statement because in my country, you can see some companies that has 4 to 5 products that they are producing and marketing. For example, you can see a commercial farmer that is focused on fish farming, pig farming, potatoes, tomatoes, and pepper, all it has different manager that is appointed but owned by one man, but there are also some people that are just focused on fish farming and yet that are also making profit but not as much as the other person.