fly-by-night
fly-by-night (2) {n.}, {informal}
1. A company that sells many cheap things for a big profit and then disappears.
A dependable company honors its guarantees, but a fly-by-night only wants your money.
2. A person who does not pay his bills, but sneaks away (as at night.)
Hotels are bothered by fly-by-nights.
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Source: A Dictionary of American Idioms