The problem isn't to find problem for which you can start a business. The problem is to find a problem for which you can start an automated business. That's much harder.
That's not the spirit of the 4HWW. The idea is to make a product that requires not much improvement, and people just buy it from your website, so essentially your 4 hours are spent doing accounting and basic customer support. You might have a part time guy to do server maintenance but that's about it. So essentially most of your revenue is profit for yourself, and you can run a "small" business with revenue in the 50-100K range.
If you start hiring full time workers, then your business has to scale a lot. Like revenue has to go to 500-1M range so you have enough to pay full time workers as well as money for yourself. That's just a completely different beast.
500-1M USD? If you hire full-time US workers then that's probably the case.
For me I hired a few remote part-timers around the world. So it costs me an order of magnitude less. And they're all awesome, so I barely have to lift a finger.