When you use the term "Duplex", you mean that it is a two story house, correct ? In the USA, the term "Duplex" means two separate living units side by side......but in other parts of the world it means a two story residence. Please clarily that you are talking about a two story single familly house...... If so, the footprint that your house will have on the ground floor will be approximately 1000 square feet. Do you need to park a car on the site or is parking offsite? If the parking is offsite, then you have lots of room for a two story, 1800 plus square foot house. The design will be dependent on your personal criteria, and it would be helpful if you could hire a local architect to help you with the layout of the rooms. It should be relatively simple once all of the factors are considered.

Please share if any duplex plan

Dear sir, Send your plan & requirements for elevation. I send best elevation according your place or requirements. Contact me. SV INTERIOR DESIGNER Sumit Makwana 8866339562

Hi You can add staircase But not in that place. It must be planned properly as structure is a key factor.