If they are to save every month for three years to reach the target amount, and each year has 12 months, they'll save for 12*3 = <<12*3=36>>36 months.
If the house's downpayment is $108000, the total amount they both save per month is $108000/36 = $<<108000/36=3000>>3000 every month.
Since they share the monthly savings, each person will pay $3000/2= =$<<3000/2=1500>>1500
#### 1500