To buy or to construct...

Dear forumers,

Need your valuable advice, yet again. After some thinking, i have decided to construct my home rather than to buy a constructed one. Can you please guide me regarding:

- what can be the total construction cost (all inclusive) for a 5 marla double story house.

- what can be the challenges during the construction process.

Also, i would like to ask. I have a 5 marla plot in i-16. Is it the right time now to start the construction or to wait?

Thanks for your valuable suggestions.

Regards,
Imtiaz