This is not a money making hobby. It will take a couple years to get close to breaking even with what you put out on a regular basis to breed them. Not to mention the jump in electric/water bills.
Don't go into this thinking you will be making money.. Expect to spend a lot of money, take up a lot of space and spend hours a day doing water changes/feedings.
This isn't an easy hobby..
As for your questions -
Culling can be done in different ways - can use clove oil, a larger predatory fish, cutting heads, etc.. expect to cull from very tiny fry to larger, almost adult sized fish. Not easy either way you do it.
Mason jars are fine - make sure they are at least 32oz as the minimum as you are wanting them to grow. Find a way to make sure you heat each one - most have a fish room that they heat up apart from the house to 85F+. So make sure to research different techniques on how to heat each one of those jars appropriately.
Live plants are better as they help keep the water cleaner, and provide food for the first day or two. But they aren't "needed".. I would look into purchasing some online because they are good to have. Otherwise, you can just use silk plants without any trouble.
BBS you will usually find easier online - San Francisco Bay online store sells them, IBC sells them in their shop, etc.. there are other places. You will want to get the higher quality, better grade.. they tend to have higher hatch rates.. it can get expensive though, I think I spent $85 on my can... but it can last a long time if kept in the fridge.
Cultures you will most likely have to find a breeder who has some for sale and purchase them from the breeder and have them shipped. Do some research on how to care for them so you know what you are prepared for.
Don't forget the IAL - makes a big difference in the health of the eggs/fry and in breeding the fish.. especially if you don't use live plants, IAL will be very good to have. That you will have to order online as well.. order it early, as sometimes customs can hold it and can take a few weeks to arrive. It's beneficial, as eggs can easily become enveloped in fungus and IAL will help prevent it.
Yes.. one for light (so they get used to it), also can use seran wrap (but can get bothersome/expensive) so I use glass canopies. They start to develop their labyrinth organ roughly at the 7wk mark and the humidity caused by the high temp + tight fitting cover will help keep the labyrinth organs healthy.
Also they help to avoid drafts... a cool draft from a fan could cause them trouble.
Don't forget adjustable heaters that can heat the tanks easily to about 84F - will need larger watts for the grow out tanks, smaller for the breeding tanks, but still able to heat warm enough.