Cher files for conservatorship over son Elijah Blue Allman.
Elijah allegedly struggles with substance abuse and mental health issues.
Court documents claim he can't manage his finances.
Cher's lawyers say conservatorship is urgently needed.
Elijah hasn't publicly commented but posted #imprisonmentviaconservatorship.
Conservatorship typically helps those unable to make decisions.
Elijah set to receive assets from late father's trust.
Concerns that funds may be spent on drugs, risking his life.
Temporary hearing set for January 5, permanent for March 6.