agree on this, that kind of project should be test, debug and deployed securely. It will take time though not years or even months but its challenging.

And as what mention above, tell your client about it, and start making the functionalities and if ever you have doubts how about you post it here and for sure many would love to help you based on what you need.

__________________
Serenity Project - 5% (Layout) - Ongoing....
Project Serenity Free Life!....