Can a gas station owner whose money is mixed with haram [earnings] due to selling alcohol and other forbidden things use such money for the cost of Hajj?
First of all, this person needs to purify his money [from mixed halal and haram earnings] through the appropriate procedure of paying Khums as explained in the Islamic Laws pertaining to the subject. Thereafter whatever halal money remains has to undergo Khums if a year has passed [and Khums is due]. After that, if there are sufficient funds remaining then he can use it for Hajj.