In my opinion, there's nothing wrong in starting a business in even the last quarter of the year. A business can get success even if it's the last quarter of the year, and similarly a business can be failed if it's started in first quarter of the year. It depends on the person who starts the business, if he/she is good at doing that business and its marketing then surely he/she will earn profits from it even if it's started in last quarter of the year.