Praise be to Allah.
Undoubtedly working in the tourist industry as it exists at present, especially in your country, involves a lot of things that go against sharee’ah, such as mixing, tabarruj (wanton display of women), alcohol and other haram things. As this is the case, part of your father’s wealth is haram. This is what the scholars call mixed wealth.
The scholars have stated that if a person has mixed wealth that includes both halal and haram, it is permissible to eat from his wealth and it is permissible to deal with him in all ways, but it is better to be cautious.
With regard to your father claiming that this is a necessity, that is not correct, because there are many means of earning a halal living. Allah says (interpretation of the meaning):
“And whosoever fears Allah and keeps his duty to Him, He will make a way for him to get out (from every difficulty).
3. And He will provide him from (sources) he never could imagine”
If a person makes this claim, then soon he will claim that he can do all kinds of haram things because of necessity.
You should understand that there are severe consequences to consuming haram wealth, even if that is only that one’s du`as are not answered, as it says in Saheeh Muslim, that the Prophet (peace and blessings of Allah be upon him) said: “Allah is Good and only accepts that which is good…” and he mentioned a man who has been traveling for a long time and is unkempt and covered with dust, and he raises his hands to the heavens (and says), “O Lord, O Lord,” when his food is haram, his drink is haram, his clothes are haram, and he is nourished with haram, so how can he receive any response? Narrated by Muslim, no. 1015.
The wealth that your father has acquired through the haram job is described by the scholars as wealth that is haram because of the way in which it was acquired, i.e., he earned it in a haram manner. Some scholars are of the view that this wealth is haram only for the one who earns it, but for the one who takes it from him in a permissible way, it is not haram for him, such as if your father gives you a gift or spends on you and so on.
Shaykh Ibn ‘Uthaymeen said: Some of the scholars said that in the case of wealth that is haram because of the way in which it was acquired, the sin is only on the one who earned it, not on the one who takes it in a permissible way from the one who acquired it. This is unlike wealth that is haram in and of itself, such as alcohol, wealth seized by force, and so on. This view has a strong basis, because the Messenger (peace and blessings of Allah be upon him) bought food from the Jews for his family, and he ate from the lamb that the Jewish women gave him in Khaybar, and he accepted the invitation of a Jew, even though it is well known that most of the Jews consume riba and haram wealth. Perhaps this view is further supported by the words of the Prophet (peace and blessings of Allah be upon him) concerning the meat that was given in charity to Bareerah: “It is charity for her and a gift from her to us.” Al-Qawl al-Mufeed ‘ala Kitab al-Tawheed, 3/112.
Shaykh Ibn ‘Uthaymeen said: With regard to that which is haram because of the way in which it is acquired, such as that which is taken by means of deceit, or by means of riba, or by means of lying and so on, this is haram for the one who acquires it, but it is not haram for anyone else if he acquires it from him in a permissible manner. This is indicated by the fact that the Prophet (peace and blessings of Allah be upon him) used to deal with the Jews even though they used to consume haram wealth and riba. This indicates that it is not haram for anyone other than the one who acquired it. Tafseer Soorat al-Baqarah, 1/198.
Based on this, then you can inherit from your father and you do not have to keep track of what he has contributed to your business, or return what he contributed, but if you are cautious about consuming any of his wealth as much as you can, that is better. And Allah knows best.
For more information, see Ahkaam al-Quran by Ibn al-‘Arabi, 1/324; al-Majmoo’, 9/430; al-Fatawa al-Fiqhiyyah al-Kubra by al-Bayhaqi, 2/233; Kashshaaf al-Qinaa’, 3/496, question no. 21701.