Is it unwise to do CPA after CA from ICAP or ICAI?

[Dard]

Salman, i would advise you go for ICAEW, rather than ICAP's C.A. The reason i am saying it because ICAEW is recognised by American CPA. You can do ICAEW in Pakistan too.
There are few things to realise
No matter what you choose, you will have to spend some money;
If you choose ICAP, you will have to wait until you clear Module D before you get a training contract of ICAP's C.A and start earning 6,500rs per month(Bearing living costs until you get a contract). Since you don't have a degree yet, no firm will induct you before module D;
Same thing for ICAEW. ICAEW's professional stage papers can't be sat in Pakistan- you will have to go dubai to give them. Only final exams of ICAEW can be sat here. Furthermore, you won't get ICAEW training contract before you complete atleast the professional stage(since you don't have a degree) Top accountancy firms have FEW positions for school leavers. If you get good grades in your high school, try those positions in the firms and get a training contract for CPA there.

[Dard]

I STRONGLY advise you to try the School leaver positions in the top accountancy firms. Be determined, hard working and focused. Involve yourself in extracurricular activities, and go for activities that prove the competences required in the top firms(Visit KPMG, Ernst and Young, Deloitte, PwC, BDO, Grant Thornton, RSM U.S websites for acadamic and competency requirements). If you fail there, my second advise is ICAEW(You can do that in U.S.A too). You will have to bear exam fee, annual subscription and tuition fee(if you go to a college)