I've bought another garage because I didn't like the location of the previous one but the game doesn't let me transfer my controlable character to it. I can do that with hired people. The old garage has only one slot in which my player is and the new one has 3 slots. I'm also level 4 if it matters. So is it possible to transfer my own character to another garage and if it is how can I do it?
In short - No it's not possible.
I had the same problem and at Steam Forum people also confirmed that. Your created character is fixed to your the base you selected at the start. You can quick jump between garages you own, but you can't change your homebase.