What is the ruling on marrying someone whose sole source of money is cultivating and selling drugs, and is such a marriage considered void?

The dowry is not a pillar of marriage according to the majority of scholars. So, if the marriage contract is concluded without a dowry, or with a corrupt dowry (such as alcohol, stolen goods, or ill-gotten money), the contract is valid, and the wife is entitled to a mahr al-mithl (a dowry equivalent to that given to women of similar standing). The Malikis hold that the marriage is annulled before consummation if the dowry was alcohol or similar substances, but after consummation, it becomes valid with a sadaq al-mithl (a dowry equivalent to that given to women of similar standing). The preponderant opinion is that of the majority of scholars because the corruption of the compensation does not exceed its absence. Growing, selling, and consuming hashish are Islamically forbidden.