Based on my understanding of your requirement, Drupal is the best platform I recommend for your project.
First reason is Drupal support the best security solution which I think is the most important point you have to ensure in such a finance based web application. Also it is the main reason that you should choose Drupal instead of Wordpress as you can easily find most people think the main reason for choosing Drupal over WordPress is the security.
Secondly, as the famous CMS, Drupal can give you a fast start of user/content management, which is also the core feature in your description.
Based on these two points above, I think Drupal is the best technique for your project. In other perspectives, Drupal also offers pretty good performance, clean UI, solid integration with 3rd party plugins, etc.
As for me, here are the highlights indicating I am the best choice for your project.
1. Full-stack developer who can solve all the problems(database/backend/frontend)
2. 5+ years Drupal/eCommerce experience
3. Expert on security problems in authentication and transactions
4. Familiar with 3rd party integrations like Facebook, LinkedIn, Google in your requirement
If you have any questions, please feel free to contact me: liuyoung2011{at}gmail{dot}com.
Thanks for your consideration.