You don't have to answer every phone call to start a side business.
When I ran Storage Squad, I had a day job. I couldn't always pick up.
My voicemail said:
“Hello, this is Nick Huber with Storage Squad. I'm sorry I missed your call. I'm probably out on another job, but I would love the opportunity to earn your business. Please leave a voicemail, send a text, or send an email and I'll get back to you as soon as I can. I can't wait to meet you. Thank you so much.”
Call them back as fast as you can. Smile through the phone. Act excited to meet people and solve their problems. Show some energy and make people feel like you actually want their business.
That alone puts you ahead of 95% of other small businesses.