Re: why there aren't more entrepreneuers here.
1) They're too busy working 80h weeks.
2) They tend to be more excited about their business than FIRE. So the goal of retirement isn't as appealing to them as it is for a cubicle monkey like me.
Re: flipping ideas
There's a tradeoff between the amount of work required to do a flip and the price of the item. You can buy a used car that runs rough for $700, replace a $30 mass airflow sensor, clean it, and sell it for a $1500 profit 10 hours later. Or you can spend 50 hours at the thrift stores looking for $3 vintage t-shirts that you can sell on ebay for a $3 profit each. The big ticket item probably sounds easier to flip than 500 t-shirts (w/ shipping and all that). This is why the landfills are full of billions of dollars worth of low-price merchandise. It wasn't worth the trouble to sell.
So basically, flip high price merchandise or real estate IF you can discover an arbitrage edge, such as knowledge of finding, fixing, cleaning, and marketing.
E.g. our state government sells retired 5 year old computers for a couple hundred dollars a pallet. They're cheap because the hard drives are wiped and because nobody needs a pallet of them. Flippers buy a Windows enterprise license, do the installs en masse, and sell them on ebay for $65-80 each to people who need one, cheap, working computer. So a pallet of nonfunctional equipment + technical knowledge + marketing knowledge = profit.
Similarly, vintage cars and motorcycles are being bought - sometimes in running condition - only to be parted out online, because the sum of their parts is worth more than the whole.
I haven't done much flipping since I had a kid and since I started making semi-good money elsewhere. I've thought about doing a few cars though, and I've also looked at RE auctions.