the.com/blank check

Trust, pre-signed, before anyone tells you the price.

means A signed check with the amount left empty, meaning the receiver can fill in any sum—or more broadly, unlimited authority or permission to act without restriction.

from Literal in origin: a bank check signed by the drawer but left with the payment line blank, trusting the holder to fill in a figure. The phrase moved into general use by the 19th century as a metaphor for total discretion or unrestricted power, as in military or political contexts—'given a blank check' to act as one sees fit.

origin
literally a signed check with no amount filled in
startup slang
SPACs raise money before picking a target
risk
you fund the destination after buying the ticket
relationship version
saying yes before hearing the plan
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