The player is bankrupt and out of the game and you get the mortgaged property with some conditions. You will have to pay the bank 10% of the mortgaged value when you get it and before you unmortgage it if it is not on the same turn.
Rules
If you have mortgaged property you also turn
this property over to your creditor but the new owner must at once
pay the Bank the amount of interest on the loan, which is 10% of the
value of the property. The new owner who does this may then, at
his/her option, pay the principal or hold the property until some later
turn, then lift the mortgage. If he/she holds property in this way until
a later turn, he/she must pay the interest again upon lifting the
mortgage.