toehold

painiote

jalansija puhekieltä A foothold small enough to support just the toe.
puhekieltä Any small advantage which allows one to make significant progress.
1990, (w), The Great Game, Folio Society 2010, p. 151:

Were Herat to fall to the Persians, this would give the Russians a crucial and dangerous toe-hold in western Afghanistan.

One in three "adult-kids" who have not left the parental nest say they are still living at home because they cannot afford to get a toehold on the property ladder by buying or renting.