down payment

käteismaksu puhekieltä A payment representing a fraction of the price of something being purchased, made to secure the right to continue making payments towards that purchase.
By extension, any initial commitment signifying an intention to carry out a larger future commitment, even though no legal rights or obligations are secured.
2009, February 5, Barack Obama, s:My Door is Always Open|My Door is Always Open

After decades of empty rhetoric, that's the down payment that we need on energy independence.

These commitments of troops, trainers, and civilians represent a strong down payment on the future of our mission in Afghanistan and on the future of NATO.