Just wanted to mention that while 40 hours billable a week is accessible, it would require working 50-60 or more. You not only have administrative tasks for your own company, but marketing your business and learning new skills to offer a higher ROA to your client will require a few hours a week. While this behind the scenes time will fluctuate, it should be pretty consistent. Marketing should be a priority weekly. Whether it's networking (online or in person) or some other form of marketing, this is an absolute necessity to keep your business thriving. It's much easier to turn clients away than to be scrambling to find new ones.
I've seen VAs with a full client load drop to almost nothing because something happened with the 1 or 2 big clients they were depending on. Because they were content with what they had, and did not market their business effectively, it took months to catch up again.
My goal when I started this business was to achieve 40 billable hours a week, but soon realized that required more hours than I seriously want to work in the long term. I don't mind putting in 60-70 hours a week for the first couple of years to develop the business, but my goal is to work no more than 40 hours a week. I think that billing 30 of those hours by that time will suit me fine.
Just my 2 cents