Im currently at the precipice of leaving my own full time job for my side job. I'm not new to entrepreneurship though so it doesn't seem all that risky. I've heard it said that when your side job makes more than your day job, you can go all in on the side job.
You sustain leads by making your customers, advocates for your business. Surprise and delight your customers with your quality of work, friendliness, and willingness to go above and beyond to serve them. Tell them your story of humble beginnings and how you serve people with your talents. Give them your business cards and ask them to refer you to friends or neighbors.
Right now I've got about $15k of work in the quoting stage and have acess to much more than that by being in proximity with other people in my industry.
That said, here's 3 tips to help.
#1 Don't go I to debt to start your business. Debt = risk. No debt = small risk. Don't be afraid of humble beginnings and finding creative solutions to get the job done.
#2 Surround yourself with people who know your industry better than you do and can provide job leads and business insights. If you are a reader, read the book 'The Proximity Principle' by Ken Coleman.
#3 Take courage and lead. Leaders serve and leaders take action. Don't be afraid to make cold calls and ask for jobs or job leads from industry leaders/suppliers.