Hi Kashif,
No problems at all.
Hiring a architect is going to be a little costly, however there are pros and cons.
The advantages are that the architect will not only prepare all the plans including designs, engineering drawing etc but will also provide recommendations related to contractors, building materials and more.
The drawback is the cost and often it has been seem that when architects are involved, the construction can take a little longer.
If you are already in contact with a good builder/contractor then most of them are experienced enough to handle the construction and can guide you very easily. If you already have a design layout in mind then you can get in touch with any draftsman and get the architectural drawing made.
At the end of the day, if this was my first house I would prefer an architect, however if I have built a house before then a contractor would do fine.
Regarding basement, the cost is going to be double of your ground floor cost, so you are looking at Rs 1500 per Sq.ft without finishing. If your plot is at 4 feet depression, then for ground floor you would need to raise it up above the road level, however if you have a basement planned then you would save a little money for digging on your basement areas, however the basements normally go 10 to 15 ft deep so digging will still be required.
If you want to keep your house scalable, even then you must plan and build your basement now. you cannot build your basement at a later stage. You can plan your house with the option that the top floor can be built independently of ground floor in terms of electric wiring, plumbing etc, the only issue will be to break your water tank and take it to top floor.
Regards,
Mustafa