It's probably not worth your time unless you enjoy doing it.
This is my opinion as well. $50 does sound kind of nice, but Temple of Sennisten requires ALOT of work if you are going to get all the skills and requirements for the quest. If your friend really wants you to do it for him (I don't blame him lol), I would demand
atleast $100, probably more.
I am not sure what the monetary value associated with the task would be. Somebody who runs a skilling/questing service could probably be more helpful in that regard. But it is definitely ALOT of work, depending on the current stats of your friend's account.
Here is a table that shows every single skill requirement you need to complete ToS:
Here are all the major quests that need to be completed to do ToS:
■The Temple at Senntisten
■Black Knight's Fortress
■Creature of Fenkenstrain
■Death Plateau
■Defender of Varrock
■Demon Slayer
■Desert Treasure
■Devious Minds
■The Dig Site
■Doric's Quest
■Druidic Ritual
■Family Crest
■Garden of Tranquillity
■Gertrude's Cat
■Goblin Diplomacy
■Icthlarin's Little Helper
■Missing My Mummy (tomb needs to be fully restored)
■Nature Spirit (needs to be started)
■Priest in Peril
■Prince Ali Rescue
■Recruitment Drive
■Gunnar's Ground (replaced Romeo and Juliet)
■Rune Mysteries
■Shades of Mort'ton
■Shield of Arrav
■The Curse of Arrav
■The Golem
■The Knight's Sword
■The Lost Tribe
■The Restless Ghost
■The Tale of the Muspah
■Temple of Ikov
■The Tourist Trap
■Troll Romance
■Troll Stronghold
■Wanted!
■Waterfall Quest
■What Lies Below
■Wolf Whistle
Additional Requirements:
■125 Kudos
■Must have completed the Abyss miniquest or have a Law Altar Teleport Tablet from the Great Orb Project.
■Must have completely 100% restored Senliten's tomb.