Black soils are very fertile soils with good water holding capacity. Generally salinity of water is associated with black soils as they are rich in sodium and supported by or compensated by calcium.There is a need to study in detail the soil and water factors.
But your desire to grow medicinal plants comes from where. Be careful about marketing problems. Any commitment by buyers is not dependable as they will avoid procurement depending and market prices. Generally sellers of planting material comitt the procurement. Many people have burnt the fingers. It is better to ask them to invest 50 % by way of cash and not by planting material as they would jack up the price and invest nothing in reality.
If you are willing to invest and cultivate and supervise your self better take the advise of a good project consultant.
with best wishes