"(Mainly I learn to never take freewheel bikes again :-)"
I have flipped dozens of bikes and not once had to remove a freewheel. Don't restrict your purchases to non-freewheel bikes or you will be limiting both your targets and profitability. Easy enough to check a freewheel before making the purchase. Or if it is bad, tell the seller you want the bike but need to lower the offer by the price of a tool and freewheel. That's a legitimate reason to bargain.