>>50692952He is incredibly busy. His interests expand from rocks to fossils, steel mons and outter space.
Unlike the other champs, he has canoncally traveled to all regions that exist except Alola. He searches for rocks and strong trainers. He used to have a house in Sinnoh but gave it to the player. In HGSS he visits museums and Silph co, which is the biggest rival of Devon. He is probably there because his dad sent him.
He is an introvert and likes to use traveling as "soul-searching journeys". He spends long times in caves all by himself.
He has a good enough relationship with his Dad. Despite living on the other side of Hoenn. Since he's going to take over Devon, he surely has some active role in the business. In the anime and manga Mr. Stone misses the times when Steven was a child and they could spend more time together. The letter he received from his dad probably dealt with some Devon stuff.
Steven isn't super competitive. He's the only champ who voluntatily resigned his title (to Wallace) and he did it just so he could hunt for rocks instead. At PWC, the strongest trainers get together in Unova to battle, but when you talk to him he says he also went there because he heard emerals can be found in Driftveil city.
In the anime he helps organize rescue missions by using Devon's funds. I'm pretty sure he earns his own money by being champ, as he is treated like a superstar by others, but his rock collection is definitely worthless. He has no diamonds or stuff, it's just rare stones that he himself finds pretty. It makes sense for someone who grew up so priviledged to not give a damn about their worth.