You don't need one to breed and i don't think you do to sell.
If you intend to sell them from a stall, you will need a street traders licence.
Yes Because to sell something any thing at all you need a licence even to sell food
You could either sell some of your guppies so as they won't breed, sell the guppy babies you have online or at yur local pet store or keep one of your guppies in one of the seperator tanks you get for your main tank.
No you do not
NO
no way you dont need a licence to sell mistletoe's
yes you need a licence to buy and sell in canada
Here are 3 options in which to make money with guppies: 1. Sell them to your local pet shop, you need to have top quality guppies that are fully grown. Your local pet shop may just take them for free because they are so easy to breed themselves. ( don't get your hopes up) 2. Sell them to friends or put up an advert in a newspaper... 3. BEST OPTION - Sell them fully grown on ebay... frozen and dead as feeder fish.
Yes
yes
With great difficulty