According to Shia, with respect to the Holy Qur'an (Ale-Emran : 97) (as a view of Shiism), the purpose of the Isteta'a (الاستطاعه) (affording to do it) is related to the following items:
1: having the financial ability,
2: having the health and sufficient power of body
3: having the safe path (besides the way be open)
4: having sufficient time for it.
Or even according to the Fatwa of Imam Khomeini as a Marja' al-Taqlid (مرجع التقلید) of Shia Islam, it is related to items below:
1: the human be complete (the age of puberty and wisdom)
2: being free (not to be slave)
3: (as we mentioned above, 3:97)
فِیهِ آیَاتٌ بَیِّنَاتٌ مَقَامُ إِبْرَاهِیمَ وَ مَنْ دَخَلَهُ کَانَ
آمِناً وَ لِلَّهِ عَلَى النَّاسِ حِجُّ الْبَیْتِ مَنِ اسْتَطَاعَ
إِلَیْهِ سَبِیلاً وَ مَنْ کَفَرَ فَإِنَّ اللَّهَ غَنِیٌّ عَنِ
In it are clear signs [such as] the standing place of Abraham. And
whoever enters it shall be safe. And [due] to Allah from the people is
a pilgrimage to the House - for whoever is able to find thereto a way.
But whoever disbelieves - then indeed, Allah is free from need of the
In the other hand (in short), Imam Khomeini illustrates that Rojoo-elal-Kefaya' is another factor. In truth, in accordance with this issue, the person who takes trip to Haj, he (after his trip) ought not to be poor to ask other people to help him…
To see the complete matter (regarding the Fatwa of Imam-Khomeini), refer to the link below.
Briefly speaking, a person (Muslim) is Wajib al-Haj who financially affords to go to Hajj. Actually he/she has so much money who be able to takes trip to Mecca(Hajj) and comes back. Besides, he/she ought to has sufficient money for himself to expense in Hajj and also he should has enough money when he returns (for the rest of his life). His family should have sufficient money during his trip and likewise when he comes back from the trip (Hajj) as well.
In other words, on the whole, his life shouldn't become deranged. (By taking trip ...) (Ayatullah Makarem Shirazi)
To see the complete texts, refer to the sources below.