Check out Odoo. Been using it for 3 years and has transformed by business. Does much more than CRM, we use it for sales, purchasing, accounts, HR and project management. But there are lots of other modules that can be added and customised. You can also have their eCommerce module integrated, not sure it would be entirely relevant to consulting but I've seen firms monetise their expertise with sessions, videos and programmes you can buy.
Would be very cheap to get started and you effectively pay for what you use so CRM would be cheap, and would give you the scope to gradually build it into a full scale ERP system to rival SAP when you're turning over tens of millions!
We have develop couple of custom CRM for client , as per my suggestion is better to have custom solution for your business. though it take little longer but it is one time fee no dependency on third party, no monthly fee . secure , salable able and reliable.
check this one out
if you need custom CRM then let's talk!
This year Smarty Software was nominated for best CRM and was called as one of the most disruptive companies of 2017. Perfect for everyone looking for a business automation solution. There are different packages available. CRM, Marketing, Accounting and Employee management. Can be purchased as combination or separately. It`s great for SME`s and the price is more than competitive.