If you get a project that takes 3-6 months you make enough money for the year and a bit left for the next year.
This means that you only need one customer to say "yes" per year. If you contact only 10 per month your success rate doesn't even have to be 1%.
What I learned is, charge per week or month and never go for full-time.
The month charging filters out all the tiny fishes and the part-time always gives you plausbile deniability when you can't answer the phone.