I can definitely agree with this. I was developing http://framestr.com (SaaS), and at the time, we had to bring on a 2nd developer and server costs were increasing (we all wanted to avoid raising funds and aim to bootstrap). Rather than raise funds, my partners and I built a small SEO business. We ended up scaling the SEO business to around $200k MRR.
Having been through the financing process before for at a previous start-up, I can say that the time invested in the side business was not a whole lot different than time invested in fund raising (+ meetings, reporting to investors after the raise).
By hustling, we were able to build a nice life style business, while being able to grow our tech SaaS. At the same time, we had much more flexibility and have been able to build / invest in what we want, and for what we believe is best long-term.
I purpose built form software for one of my digital marketing clients that integrates with Slack, Asana, Mailchimp, Campaign Monitor and Zendesk. It has built in conversion tracking for Adwords / Analytics, A/B Testing and SPAM filters.
I recently developed/launched http://framestr.com. It's an online form software that I developed, originally, for a few lead generation websites that I own. It currently generates around $950 / month.