Is Hajj obligatory for someone who possesses only a small amount of money that barely covers the basic expenses of Hajj, has no children, has only a wife, and earns a low income?

If you are physically capable of performing Hajj, have the financial means for it, and find a mahram (definition) or a trustworthy companion, then you must perform Hajj immediately. This is because it is an immediate obligation according to the majority of scholars, based on the Almighty's saying: "And [due] to Allah from the people is a pilgrimage to the House - for whoever is able to find thereto a way" (Quran 3:97), and the Prophet's (peace be upon him) saying: "Whoever intends to perform Hajj, let him hasten, for indeed the sick may fall ill, the lost may go astray, and a need may arise."