If you look at this as a job, then I think you will have a hard time sticking through all the ups and downs.
Well, I know people, who nowadays live off of their Hive income (at least one, @jlufer), but I have not seen anyone so far, who would see playing Splinterlands as their job.
Is there anyone nowadays, who can make a living with Splinterlands?
Lots of people play Splinterlands only as a game to earn and not to enjoy the playing itself, maybe you can't live only with Splinterlands unless you invest a big quantity of money, but for sure you could consider it a "second job" if you are enough "big" as a player.
But if you only think about earnings, you will lose the joy of playing in my opinion