There are a lot of people in your situation. Try keeping your job (even though you hate it) until you can sell the agency. Buy a guitar as soon as you can afford one (and not a real cheap one; they sound horrible!), then play at open mics in the evenings for your own enjoyment and to build your name. After a year or so, evaluate your options once again.
One step at a time gets you to where you want to be. Leaping without a landing place only brings trouble.
Sincere best wishes,
AB