What can a young man who abides by Islamic teachings do to control his sexual desire in case he cannot marry or observe Sawm (fast)?
If the case is as you have described, there is no harm in postponing his marriage until he can afford it. Allah (Glorified and Exalted be He) says,
Allâh burdens not a person beyond his scope.
However, he should fear Allah as He should be feared and abstain from the things which He prohibited. Allah (Exalted be He) says,
And let those who find not the financial means for marriage keep themselves chaste, until Allâh enriches them of His Bounty.
(Part No. 18; Page No. 21) May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.