$40K is not much to put into a business. You'd likely be putting down more than that just to open a convenience store.
Sure you need to spend a lot of money to grow a $1B+ business, but the same is true for a $100M business or a $10M business and even most $1M businesses.
$40k is a lot to put in a business you have no idea if it can make money or whether it is needed.
It's a definite that people have to eat. I would assume most failures in restaurants and convenience stores are operations, not a critically flawed business model.
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But yes, I guess $40k is less than $2M, but it also takes $40k away from another venture and possibly having to go back to a day job to take another run at something.
All because you didn't validate the problem before cutting off your income source.
You would not need to put up a lot of money if you just came to a market to sell some vegetables. For less central areas you could potentially sell stuff for free. Convenience store is a bad example as these are heavily standardised by now: we all expect a high diversity of products and thus the equipment needed to store it
Sure you need to spend a lot of money to grow a $1B+ business, but the same is true for a $100M business or a $10M business and even most $1M businesses.