The number of hours per day to spend on your business depends on the type and nature of business you have.
As a business owner you should spend as much time as possible for your business, If you are doing part time business, like a student or housewife, try to spare about 3-5 hours per day for your business. If you are into fill time business, then spend as much time as possible for you, ideally 8-10 hours are enough for a business.
Nowadays every business needs a website because a website is one of the best way to attract more customers. You can build a website very easily by hiring web designer and make it available on the web with the help of web hosting service.