

Narrated Hz Sahl bin Sa rz.a: While we were sitting in the company of the Prophet s.a.w a woman came to him n presented herself (for marriage) to him. The Prophet s.a.w looked at her, lowering his eyes n raising them,but didn't give a reply. One of his companions rz.a said, "Marry her to me O Allah's Apostle!" The Prophet s.a.w asked (him), "Have you got anything?" He said, "I have got nothing." The Prophet s.a.w said, "Not even an iron ring?" He Said, "Not even an iron ring, but I will tear my garment into two halves n give her one half n keep the other half." The Prophet s.a.w said,"No. Do you know some of the Quran (by heart)?" He said, "Yes."The Prophet s.a.w said,"Go, I have agreed to marry her to you with what you know of the Qur'an (as her Mahr)." 'And for those who have no courses (i.e. they are still immature). (65.4) And the 'Iddat for the girl before puberty is three months (in the above Verse).(Bukhari,Book #62, Hadith #63)
This hadis proves that marriage is very easy to perform but unfortunately, now a days fornication is easy n Nikah is difficult.
First, the boys have to get good education which enable them to have either high paid salary job or well established business before they can think of marriage, the same a girl wants.
Allah swt has made human bodies in this manner that one needs the 'company' of opposite gender at one stage. Which is why unmarried young ppl involve in fornication, especially, teenagers are highly vulnerable-who, even want to restrain though, find it too tough to struggle with themselves.