During any early business beginnings, my #1 tip is to have a part time job. Something easy. Where you can make quick money on the side. Bartending, waitering, sales rep... I was a nanny, for example! Something that will let you "check out" when you aren't working. Which won't consume your mind. But will provide you enough income to make it through the month.
With this basic salary you'll be able to breath, you won't struggle, so you won't panic. YET, you won't want to be stuck working in that type of job forever (not even part time) so you'll want to push your business.
Tip #2: with zero to little clients, you'll have free time. Just remember: No time is free time. Work on YOURSELF!!! Organize your days, teach yourself Self-discipline and work-ethic, write, brainstorm, update your portfolio, keep learning... all of these will help you grow and maintain clients later on. Invest in researching, reading, attend weminars, seminars, workshops... or my online coaching classes for business & life!
Tip #3: during your "down time" get out and search for new clients yourself, be active, get new contacts and connections, network. Let everyone know what you do. Create your own opportunities to find those new clients. No one else will do it for you and they won't come to you.
Tip #4: work on your personal brand. Create a website, write about yourself, build your social, grow your social media following... See my tips here.