Trustworthy salesman

When Trustworthy Salesman enters the battlefield,
you may cast an artifact card from your hand
with a mana cost of 4 or less without paying its
mana cost. If you do, put two time counters
on that artifact. At the beginning of each upkeep,
remove a time counter from each artifact you
control. When the last time counter is removed
from the artifact, sacrifice it.
-"Yes, yes! good quality!"