All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
First of all, we thank you for this confidence and for this endeavor in which you seek to gain lawful earning from the transactions that you want to carry out. This is indeed the matter of a Muslim.
So, may Allah reward you for your endeavor and prepare for your affairs right guidance.
As regards what you asked about, which is providing financial advice in return for a commission that you take from the one who seeks this advice, then there is nothing wrong with it if it does not involve any help in what is forbidden; Allah Says (what means): {…but do not cooperate in sin and aggression.} [Quran 5:2]
If you know that a specific person wants consultation to do something forbidden, then it is not permissible for you to cooperate with him in that. However, if you do not know the intention of the person, then you do not have to investigate about him and find out whether his transactions are lawful or forbidden as long as the subject of counseling is permissible.
It appears –Allah knows best –that the fee for providing consultations should be based on fixing a period of time; so your work is like a private hired person and you deserve the wages for making yourself available during the time period agreed upon even if the person who hired you did not benefit from the service.
The Kuwaiti Fiqh Encyclopedia reads:
"The private employee is a person who does a temporary work for a specific person, and his contract is for a (limited) period of time. He deserves the fee by making himself available during this period of time; because his benefits are due for the person who hired him during the period of the contract.”
The adviser is a trustee (that is to say that he is trusted about the matters which he is asked about), and he must be sincere in his work and he should do it in the best manner.
‘Aa’ishah narrated that the Prophet said: “Allah loves that if one of you does any type of work that he does it perfectly.” [Al-Bayhaqi and others; and Al-Albaani said: “It is a Hasan Hadeeth.”
Allah knows best.