Horseplayer (1990)

Bud is a strange loner who works in a liquor store by day and is addicted to betting on the horses at night. He lives in a low-rent building in an even lower-rent section of town, and one day a couple, who appear to be brother and sister, move into Bud's building. Soon the sister begins to try to seduce Bud, but not for the reasons one would expect, as she and her "brother" aren't what they appear to be--but neither is Bud.