It is permissible for a woman to marry a man who is known to be unable to have intercourse, because intercourse is her right but she may waive it. If she does that then she cannot demand this right after marriage. 

Ibn Qudaamah (may Allaah have mercy on him) said in al-Mughni (7/142), after mentioning faults which give the wife the right to annul the marriage, including the husband’s inability to have intercourse: One of the conditions of allowing the option (of annulment) because of these faults is that he did not know of it at the time of the marriage contract, and he did not agree to it afterwards. If he knew of it at the time of the marriage contract or he found out about it afterwards and agreed to it, then he does not have the option (of annulling it). And we do not know of any difference of scholarly opinion (concerning this). End quote from al-Mughni (7/142). 

In al-Mudawwanah (2/144) it says: I say: What do you think if she knowingly marries a man whose penis has been cut off or a eunuch? He said: She does not have the option (of annulment), and Maalik said likewise. He said: Maalik said: If she marries a eunuch and did not know of that, then she has the right to annulment when she comes to know. End quote. 

See: al-Mawsoo’ah al-Fiqhiyyah (29/69). 

Although we have said that it is permissible to marry him, it is better for you not to marry such a man, because intercourse and what it leads to, namely having children, are natural things that men and women need. You may be willing to give up this right now, but you do not know what will happen in a year or two, and marriages are supposed to be permanent. 

Hence Imam Ahmad said to the guardian of a woman: I would not like you to give her in marriage to an impotent man. If she agrees now, she will dislike him when she enters upon him, because intimacy is something to which they are naturally inclined and they like what we like. 

Ibn Qudaamah said, commenting on that: That is because the harm caused by that will be ongoing, but acceptance of that cannot be trusted to be ongoing. It may turn to resentment and enmity. 

Al-Mughni (10/67). 

It is obvious that this man is a stranger (non-mahram) to you, so it is not permissible for you to form any kind of relationship with him, until the marriage contract is done. 

We ask Allaah to help and guide you, and to make goodness easy for you wherever it may be. 

And Allaah knows best.