I can answer what my Dad used to do on top of just negotiating his player's wage for them upon transfer or contract renegotiation (for which he never really made a penny from).
Sort out pretty much every single admin aspect of the player's lives.... Insurance, passports, mortgages, pensions, investments, driving licenses, utilities, bills to be paid, etc, etc.
Reach out to, negotiate and agree terms with external sponsors (sportswear, luxury brands, motor companies, etc).
Manage the player's diary for outside club commitments (everything from guest appearances to booking driving lessons).
Keep in contact with clubs and other agents re: needs and wants of various clubs across the country and, indeed, all over europe and beyond.
Deal with the police and CPS for potential prosecutions and often foot any legal fees (yes this was a thing that happened sometimes).
Maintain good contacts in the press to get the right stories in there at the right times for their players.
Find new clubs for players who are being/have been released.
Sort out paperwork and find clubs to help them go through coaching badges.
Sort out guest tickets for players' family and friends at matches.
If I asked my Dad he would probably tell me literally tens of other things that he used to do for the players he represented. Remember for every player represented at the top end where the agent makes a lot of money, the agent is likely to represent tens of players at the bottom end of the scale for which the agent does a lot of work and makes nothing. Most of the players my Dad represented did not have a father who played an active role in their lives, nor any well educated close friends or family members who could give good advice and guidance, so these young men were cannon fodder when it came to negotiating contracts with clubs (or sponsors), who would take advantage whenever they could.
My dad jacked it in when the concept of 'registered agents' was brought in, along with the agent having to pay a reasonable lump sum to be registered. This was supposed to regulate the practice and stop rogue agents. However what it did instead was cause many of the honest agents who were looking after just a few players, not really making any money and typically acting in those players best interests to cease practising, allowing the super agents to hoover up more players. Personally I think my Dad should've started to charge just a small, modest percentage of each player's wage, paid the fee, registered and continued to practice as he was good at what he did and a large majority of the players he represented seemed to really appreciate him (a few who left for big agencies asked to come back). However he said he was never in it for money and would've felt bad taking money just for helping young men who didn't have many good influences in their lives. Though he did carry on doing some consultancy work on player contracts for several years (including for some pretty big agents/agencies) for which he finally actually made some decent money (which he absolutely deserved IMO).
To be a good agent you typically have to have legal qualifications (or have a legal team), be a good negotiator, a good organiser, manage lots of rather disfunctional family figures, maintain loads of contacts and be prepared to work bloody hard at pretty much all hours.
I don't know how the likes of Raiola and the Super agents operate these days but I suspect their MO involves them having quite large outgoings in paying money to the families of young talent located all over the World to get them on the books. A large majority of that young talent will then never earn a penny from the game.
