Is jihad obligatory for one who does not possess money to travel for jihad and owes debts to another Muslim? And must he pay off the loan first, or should he go for jihad if he obtains money and jihad is a necessity?

If Jihad is Fard Ayn (an individual obligation), then the creditor's permission is not required for going forth, unless the debtor leaves behind enough to pay his debt, or provides a guarantor, or secures his debt with a pledge. However, if Jihad is Fard Kifayah (a collective obligation), then it is not permissible to go forth without the creditor's permission. If the debtor possesses what fulfills his debt, then if Jihad is Fard Kifayah, the payment of the debt takes precedence. But if Jihad is Fard Ayn due to the presence of the enemy or the battle line, Jihad takes precedence. However, if Jihad becomes obligatory by the Imam's command, then the payment of the debt takes precedence.