I doubt people write business plans before they decide on whether the business is a good idea .... one step at a time buddy
Actually a business plan is a good basis for beginning. It will help you to determine if you have enough knowledge and competence to make the businesss profitable. It will help you to answer many of your questions. Also, renderfarms requrie a substantial amount of knowledge and tend to be provided by business running other ventures along side the farm. Do a bit of research and determine if you feel that the venture is viable.