Green’s Dictionary of Slang

(US) a notional club that took advantage of the US government’s payment to ex-GIs of $20/week for one year (52 weeks) or until they could find a job.

1946		Time 26 Aug. 17/3: General Omar Bradley had sharp words for the ex-doughboys who would rather stay in the 52-20 Clubs (drawing $20 a week for up to 52 weeks) than take low paid jobs.
1951		J. Havighurst Amer. Veteran Back Home 148: These younger kids had it tougher than us older fellows. Most of them [...] signed up for the 52-20 club because it looked like a free meal ticke for them, not having to work for itt.
1965		L. Bruce How to Talk Dirty 27: My real reason for going to the Veteran’s Administration [...] was the 52-20 Club. The Government gave all ex-GIs $20 a week for a year or until they could find a job. The accepted smart-thing-to-do was to find an employer who didn’t report your wages [...] then you could grab the $20 plus your salary.