Land related laws for greenhouse cultivation

Im situated in Punjab and am interested in greenhouse cultivation. i dont possess any land for agriculture but i do have more than 5000 sq. ft. of open roof space with ample sunlight. The main queries i have are:

  1. Is use of agricultural land necessary to be able to avail incentives and subsidies in Punjab?
  2. Are building allowed to be used as greenhouse space by government and do they give subsidy for these kind of situations?
  3. Is it suitable to use roof structures as greenhouse space as hydroponics is going to be used?
  4. What are the state and national incentives and subsidies being provided by the goverment?
  5. What will be the approximate cost of setting up a 2000 sq ft greenhouse using hydroponics and hi-tech equipment?