Ah now I can see why The Queen has told Charles and William to sort it out. When Charles becomes king hw will still support The Sussex household, William gets the duchy of Cornwall for him and his heirs. Harry wouldn't be answerable to his brother for income till his brother becomes king.
Once Prince Charles becomes king, the Duchy of Cornwall will be inherited by Prince William for him to support his own family as it grows. Prince Charles will then take on the Duchy of Lancaster.
The Duchy of Lancaster is a private estate, consisting of 18,433 hectares of private land across England and Wales, which is currently owned by The Queen. It comprises commercial, agricultural and residential properties, in addition to a significant portfolio of financial investments and urban residences.
The net value of the Duchy of Lancaster is around £518.7 million to which The Queen receives about £19.2 million to fund her family. As of this point, Her Majesty uses that money for working members of the Royal Family like the Duke of York, Princess Anne, and the Earl and Countess of Wessex.
When Prince Charles takes on the Duchy of Lancaster, it will be his duty to then support the Duke and Duchess of Sussex through it, including other senior working members of the family. It is well known that Prince Charles’ vision of the future includes a slimmed down version that already cuts out his nieces, Princesses Beatrice and Eugenie and could consist of his own siblings as the years go on.