On top of all that RavensGryf has said above, you should also know that breeding budgies won't make you any money. It will likely leave you in the hole.
Buying proper breeding cages, nest boxes, bedding, food, emergency supplies for hand feeding (Plus the knowledge of how to do this!) vet bills..... And then trying to find suitable homes for your birds is sometime a challenge depending on where you live.
Just all things you'll need to think about.