Repose confidence in the understanding or discretion of a madman

[Mher]

Again hardships in grasping Poe's mental direction. What does he want to say by the underlined part? What is "discretion" here?

"To repose confidence in the understanding or discretion of a madman, is to gain him body
and soul. In this way we were enabled to dispense with an expensive body of keepers."

Repose-recover?
Discretion-?
gain-give?
expensive-a lot?

[Charlie Bernstein]

Again hardships in grasping Poe's mental direction. What does he want to say by the underlined part? What is "discretion" here?

"To repose confidence in the understanding or discretion of a madman, is to gain him body
and soul. In this way we were enabled to dispense with an expensive body of keepers."

Repose- to place, to put
Discretion- the good judgement, good behavior, trustworthiness
gain- win him over, earn his confidence
expensive- costly

To put your faith in the good judgement of a lunatic is to win his good behavior. That's how we were able to care for him without paying a lot for doctors, nurses, or jailers.