If both parties are agreeable to partition property that is joint with right of survivorship, will it still be a costly expense in court. What would l

If both parties agree, I would not use a partition action.  If both parties want to split the property physically, you would obain a survey with the legal descriptions, obtain local government approval for the split if required, and then both parties would sign deeds of the land to go to each party.  That would be very simple, with no need for a partition action.  If both parties want to sell the property, they can proceed with a sale without going through a partition action.  A partition action is useful when one party wants to sell the land and the other will not agree.  With joint tenancy with full rights of survivorship, a partition action is available but of limited utility because the survivorship interest cannot be broken.  This means that all the court can order sold at auction is the life estate interest of the joint tenants, but when all but one joint tenant have passed away, the property vests in the last surviving joint tenant.  Not a lot of buyers for that sort of interest.  All parties are much better off if they can agree what to do with the property, and in that situation, you don't need a partition.