I believe that Hajj is compulsory for those who have the means to perform it. However, I read somewhere that once you perform Umrah, it becomes compulsory, no matter what, to perform Hajj. Is that true? Because someone I know is hesitating to perform Umrah for the reason that they might not be able to perform Hajj after that. So they are, in my view losing the opportunity to perform Umrah.
Hajj is obligatory on those who have the means to go for it:
In it are signs manifest; (for example) the Station of Abraham; whoever enters it attains security; pilgrimage thereto is a duty men owe to Allah those who can afford the journey; but if any deny faith Allah stands not in need of any of his creatures (al-Quran, 3:97)
It is commonly thought that if you can do ‘Umrah then you have proved your material ability to do Hajj as well. And if that is true, you should do what is obligatory, i.e. Hajj, and not what is just supererogatory (nafil), i.e. ‘Umrah. However, if it could be shown that while doing ‘Umrah is possible for an individual, doing Hajj is still not materially possible, then one can do ‘Umrah even without doing Hajj first. Personally, I find it difficult to appreciate how could it be possible for an individual to do ‘Umrah but still not be able to plan seriously for Hajj. I know that the expenses for ‘Umrah are much less, but one can still save more to do Hajj instead of spending the amount on ‘Umrah and start collecting funds for Hajj all the way from scratch.