It's easy if you go about it the right way, it just doesn't guarantee success...But if you have a job, and can support yourself working full time, you can just have a grow on the side and work you ass off both working full time and growing full time as well. That way, if you fail bigtime, or can't sell your meds anywhere, you still have a job to fall back on.
Once you get the grow dialed in, and you're making more money than you would be working your regular job full time, you can quit your regular job and just grow.
If you can harvest 2 pounds of dank top shelf buds a month, you can pay your rent and utilities, and still end up with between 15-30K a year depending on overhead and quality. Gonna take up at least an entire bedroom in a house.