I'm just going to add one thing to this comment, which is really good.
I believe this is the approach most solo devs take. But it's important to note that, specially if you're taking the fiverr route, making sure the art/music is cohesive for the whole game is crucial.
For this asset per asset method to work, you have to work with the same person to ensure consistency. They have to be involved in the game somehow to understand what you're trying to make.
Just giving people a brief from time to time of what you're trying to make is not a good plan. So communication is very very important with this approach.
Good luck!