Sounds Ideal, but I have no knowledge about the system design. Cannot figure out what should I suggest.

If you can do it yourself, then you can absolutely save your budget.

Ok, I will bite on this one. When you are looking for heat exchanger parts for stuff under a ton in size, you're talking about window air conditioner and dehumidifier parts. Below that is refrigerator parts. Above a ton, under 2 tons, you're talking about car and van AC parts.

You will find that the main spec for these parts is the noise they make. Other than that, water conducts heat better than refrigerant. So there you go.

just how profitable it is

How about calling a professional and discuss with him about the capacities of the AC and heater and the factors affecting its performance.