I agree with Colin. I started a second site before my first site was making decent money and my split focus made both of them grow more slowly. If you’re not outsourcing anything, build one until it’s making you some money to outsource at least some of the work. I wish I’d done it that way.
My main site was decimated by the HCU and not seeing recovery despite a lot of updates. No new content is ranking either. My second site wasn’t hit by the HCU and traffic has been increasing quickly for several months.