Is there anyone who can help in developing an individual CRM system for a niche site?

Question

CRM

The question is not a fake one, so I apologize for possible, not correct, oversights.
I work in an agency (I have already applied here for help), my duties do not include solving technical issues, but as usual, the boss asked - so you need to figure it out.
We were approached by a company for the services of BTL direction, they themselves are engaged in outdoor advertising. In the course of the case, they asked themselves the question of changing the "inside" of the site. Take the boss and blurt out, they say, of course we can.
Hence the question arises - is it possible to organize the so-called self-written crm, subject to a compressed budget?
The current site is www.globalrise.com.ua , the main thing is how much it will cost and in general the game is worth the candle, if in fact not fake people undertook to organize it?
Thanks in advance for the constructive comments!