“What business requires very little skill except hard work but you can make at least $500,000 a year?”
No legal business. $500K/yr is the 99.5% point in the US income distribution. If hard work was all it took, there would be a lot more people making that much money. Generally, the more money you want, the more skills you need, along with working harder.
Notice I said: no legal business.
With one possible exception: prostitution. My authority for this is an article in The Economist, from 2014, examining the online sex trade. They found the average cost of an hour with a woman was $250, with a range of $200 to $400 in different cities. $500K per year is $1369 per day, so a prostitute who had 4 - 7 clients per day, every day, or who could charge above average prices for whatever reason, could earn $500K/yr. That certainly counts as hard work, but doesn’t need a lot of skill as most people define it. Prostitution is not legal in the USA, except for parts of Nevada. But it is legal in some nice places, like England, Holland, and Australia. Disclaimer: they said rates vary a lot, because supply and demand vary a lot, and rates have been trending downwards lately. Do your research before committing.
You may need to subscribe to The Economist or buy a short period of access, but here is the link: