I met a person by Internet who wants to marry me. He has been living in US and has committed fornication. I have committed sin by thinking about sex; although I try hard I sin in my mind. It is for the reason that I want to get married soon. I do not talk to him about sex, its nothing of the sort. It is said in Qur'an that "for the adulter is the adulteress". Does this apply to me? I sincerely want to be better Muslim and also want him to be the same. May be through each other we will overcome the Satan? I pray to Allah to give guidance and light to both of us, but have gotten very confused whether it will be right by Islam to marry him. I know its very important that he realizes and repents, which Insha Allah I will make sure before taking a decision, the thing which made me consider him was that he is ready that we'll take care of my parents whom I cannot leave alone as both are sick and would be lonely when I marry. Another is that I feel maybe Allah has given me this chance, to make my faith stronger and help bring back a lost Muslim to the right path. I sincerely pray to Allah fort that. Needing guidance from my siblings in Islam.

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.

It is unlawful for you to accept this man as a husband unless you know for a fact that he has repented from Zina (fornication or adultery) and that he is now a religious and pious person with a good character.

Allah Says (what means): {The fornicator does not marry except a [female] fornicator or polytheist, and none marries her except a fornicator or a polytheist, and that has been made unlawful to the believers.} [Quran 24: 3]

Moreover, the Prophet said: “If a man whose religiosity and moral conduct are pleasing to you proposes to you, accept his marriage proposal; otherwise, there will be Fitnah (temptation) and great mischief on earth.” [At-Tirmithi and Ibn Maajah]

Know also that there is no good for you in this man as long as he keeps on committing Zina, which is an obnoxious sin.
In addition, a lot of problems might happen between you. These might lead to separation and divorce because of the sin he keeps on committing.

If you fear Allah and be patient, Allah will Give you a good pious man better than the one you mentioned. Allah Says (what means): {And whoever fears Allah - He will make for him a way out. And will provide for him from where he does not expect.} [Quran 65: 2]

Allah knows best.