How can I start hydroponics farming on a small scale. What all is required to start such farming?

You can do hydroponics in an organic sense, by deriving all the plant nutrients you require from composted materials, be it grass clippings, manure, straw, tree leaves.

These are digested and then water of the hydroponic system is recycles through the compost.

Some compost will have  ratios of nutrients far different from the pants you choose to grow, so that a wide variety of substrates is better than a single source.

Hydroponic gardening is almost exclusively done inside  buildings in the north,( particularly if the crop is pot).

You can go al purchased chemical fertilizer, including all the micro nutrients. That does require knowing closely the ratios of  nutrient this crop will need.

Using a layer of sand on the hydroponic bed assists in distributing the fertile water, makes it easier to ensure that plants are getting their minimum.  Using this strategy a simple vapor barrier below the sand becomes a low cost hydroponic bed. You could even do it outside in summer. The sand protects the plastic sheeting from sunlight.

Using sand means it is not soil-less. But soil-less is not a central concept. If you want to grow potato crops hydroponicaly you will have to use something to keep the sun off the tubers. Sand works fine.

Hydroponic growers typically strives to avoid loss of water of transpiration. That can raise humidity to unhealthy levels.  Heat build up can also be a problem.

Also, inside a closed space plants tend to use up all their CO2 unless we are supplying outside air or a source of CO2.

How small of a scale are you envisioning.  When doing some agricultural research, I could grow full--size corn plants with full-size ears in an 18X18X12 inch stainless steel pan.  I designed a custom nutrient blend, used deionized water, and (surprisingly) did not have to aerate the nutrient solution.  So, you can start really small.  Contact your local University Cooperative Extension Agent.  He or she will be able to direct you to information and resources on hydroponics.  As you grow your hydroponics enterprise, keep in mind that when you change out the nutrient solutions, you will have to have a plan for disposing of the used-up nutrients properly -- you can't just dump it out on the ground and/or down the sink or storm sewer.