fly-by-night

nouns

a debtor who flees to avoid paying
is a type of (narrower)
a person who owes a creditor; someone who has the obligation of paying a debt

adjectives

(of businesses and businessmen) unscrupulous
"a shady operation"
ephemeral
"the symphony is no fly-by-night venture"
is similar to
not permanent; not lasting
"politics is an impermanent factor of life"- James Thurber; "impermanent palm cottages"; "a temperary arrangement"; "temporary housing"