In the real world, well in England, when a player is given his first pro contract it will be either a short 2 year contract on low ages, this is usually when a player is brought into the squad but needs a lot of work still to be done and will probably spend most of that time in the reserves, with the odd appearance in early round of cup games.
In this game that would be your 2* player

The second would be say a 4-5 year contract, wages on slightly lower than regulars the same age in the squad, with increases through the term of his contract when goals are achieved, first team appearances and such like.
This would be the 4*.
In both cases a signing on fee would be paid.
IMO the tokens '24' is the signing on fee or agents cost, but as I said above, it is totally unrealistic, as the money you can get from the bank at level 3 is 6m.
A 4*27 will cost around 3.5m and maybe 20 tokens with wages of around 40k.
Real cost
Cash up front 3.5m
Token cost 4.8m
Wages 120k
Total 8,420,000

Nordeus way.
24 tokens 5.76m
Wages 120k

So you save around 2.5m, but only if you have to bid 20+ tokens, if you get him in the auction for 10 or less then you have the better deal, factoring in the cost of building the facilities and you are losing money big style.
Buying from Nordeus and selling does not really work well either financially as you would have to sell him for over 6m.
6m is useless to you as your token tally has been reduced to get him in the first place.