I wouldn't say it is free money; you still have to manage them & your team as well. With a profit margin of 5%, the margins would be too close for comfort for me/not worth it if I had a private practice. But if you can get the profit margins higher 25% or so, it would be worth it to me.
But I agree that the PE groups just purchase practices for insane prices that a new grad or anyone would ever pay. Not sure if anyone is familiar with the online space/DTC on these forums. But if you have an online DTC company selling products such as supplements, the profit margins on it will be around your 5%-10% after everything if you are lucky. So if you are doing $10M in revenue, you will likely only make around $1M.
However, what is really interesting is when DTC companies sell to a PE or larger companies. They purchase them on multiples of Revenue, not EBITDA. Small-Mid size DTC brands ($10M-$30M in revenue) will generally sell for 3x-6x revenue (this can vary because of many factors). So a company producing $15M in revenue and only profiting $1M the company would likely sell for/be worth $45M (give or take). It is also significantly more scaleable than dentistry.