Turning Wordpress into a Freelancer Powerhouse

I'm currently doing an article for a major outlet on how freelancers could use Wordpress to roll out their own self-hosted invoicing, CRM and project management systems rather than paying a ton of money for subscriptions since many professionals already have significant server resources.

Anyway, I'm looking for suggestions on plugins & tools worth profiling - so any insights are greatly appreciated.

Thanks very much in advance!