Is it permissible to take a "Qard Hasan" (interest-free loan) to build an apartment for the purpose of marriage, knowing that the questioner lives in the family home and does not have the financial capacity to build?

There are two types of loans: a good loan (Qard Hasan) with no interest, which is unanimously permissible, and it is recommended to lend it and permissible to borrow it. The second type is an interest-bearing loan, which is usury (Riba) and is unanimously forbidden, considered among the major sins, and only dire necessity makes it permissible. Building an apartment for marriage is not a necessity that permits usury as long as renting is possible. Patience with celibacy is better than marrying with usury.

Allah's help is hoped for the one who seeks marriage for chastity, as marriage is a cause for richness, as stated in His exalted قول (قوله تعالى): (And marry the unmarried among you and the righteous among your male slaves and female slaves. If they should be poor, Allah will enrich them from His bounty; and Allah is all-Encompassing and Knowing.)