down payment or paid in full?

"Now it is God who makes us stand firm in Christ. He anointed us, set his seal of ownership on us, and put his Spirit in our hearts as a deposit, GUARANTEEING what is to come." 2 Corin. 1:21-22

The notes in my Study Bible mention this deposit of the Holy Spirit as a sort of down payment on the eternal life that is yet to come. I'm not sure I agree with that assessment? When I make a down payment on a car or a house I am promising to pay the rest of the cost in the future. In the spiritual realm the cost has already been Paid in Full!

It's amazing to me that God would go beyond all he did through the cross and in addition send his holy spirit to bless my life in the here and now. A promise of greater things to come. A daily reminder of eternity with him. A moment-by-moment helper to insure his LIFE in me here on earth until I enter eternal life in him one day.

The Message says it this way: "Whatever God has promised gets stamped with the Yes of Jesus. In him, this is what we preach and pray, the great Amen, God's Yes and our Yes together, gloriously evident. God affirms us, making us a sure thing in Christ, putting his Yes within us. By his Spirit he has stamped us with his eternal pledge—a sure beginning of what he is destined to complete."