This basically the premise to Richard Pryor's movie "Brewster's Millions" except that one of the rules was that you cannot buy or own anything. At the end of the month you must have spent the money and have nothing to show for it.
The answer is politics. Spend it all on a political campaign.
The political campaign is actually the innovation of the film, which was an adaptation.
ending
And then he realized that winning would break the rules, as the salary makes the position considered an asset, so he campaigned for "none of the above". At the end of the movie, that option wins.