To keep some money back for possible expensive problems in the future.
salt away
To save or preserve (especially money) for future use.
go the whole hog
To do something as completely or entirely as possible; to hold back or…
give back
To contribute money, goods, or, especially, services for charitable pu…
set back
To cost money.
live paycheck to paycheck
To have the entirety of one's earnings consumed by living expenses, th…
save something for a rainy day
To save something just in case one may need it.