Hi
There are 3 types viz., Low cost, medium cost and high cost green houses
The expenditure ranges form Rs. 400 - Rs.2500 per sq. mt depending on the type
Better visit few green houses in your locality and get some first hand info from the growers before you start
You can grow high value crops like Roses, Gerbera, Carnation, Colored Capsicum, English Cucumber, Indeterminate Tomato etc
Regards
Harish