RWCPA and M123,
It takes a few years to ramp up. You're building your revenues via arithmetic growth, so you pick up, say, 15 good clients year 1, add another 15 year 2, another 15 year 3, and so on. Progress is slow but should be steady.
This is a GIGANTIC topic, but you almost more than anything else need to have two or three marketing efforts you go really strong on and which get you good quality, profitable clients… then, whatever works, you do LOTS more of that.
This caution: The mistake new solo CPAs make is focusing on revenue rather than profit. That seems smart short-term. Why not attract (say) 500 $200 tax returns… you'll work like a maniac but instantly make maybe $75K… Problem is that's not a profitable practice. You'll essentially be working double shifts making $30 an hour. Further, when the superb client comes along and they are willing to pay $300 an hour, you'll have tools and a practice model that isn't the right approach for them.
This is why I say you want to consider buying a truly profitable firm. With that model, maybe you make (say) $150K a year… though use $50K of that to pay off the loan… but then a few years down the road have the entire $150K all to yourself.
Some people in this situation will also have decided it's worth it to figure out how to double or triple the $150K a year so they're making $300K or $450K.