It is mandatory for organisations employing 30 or more persons to have apprentices. Normally the number of apprentices which can be engaged in each trade is in proportion to the number of regular employees in the respective trade. Within a financial year, each establishment shall engage apprentices in a band of 2.5 % to 15 % of the total strength of the establishment. There are some designated trades but you can have optional trades where you can have apprentices.
Please note that engaging apprentices should not be taken as a measure to reduce cost. Apprentices are learners, and there are some restrictions on their employment, with regard to hours of work, overtime working etc.