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.