Got Accepted, might turn it down. Is that crazy?

For context here, I currently work as a non union residential service electrician, applying for the inside wireman program. I gross about 90k a year with my job, benefits are just basic medical & dental with a 3% match for the retirement plan. My boss is super cool too which makes it harder to leave.
I also have an LLC as an electrical contractor on the side which pulls in about 3,000 a month profit, with a lot of upside. In the future, the goal is to open up my own shop, whether union or non-union, i don’t know yet. But for the time being I want to gain more experience before that time comes.
On the flip side I would love be a part of the union and get a solid education and top tier training. However, the work outlook in my area is pretty bad and 1,000 guys are sitting on the books with apprentices being laid off for half the year.

Choosing to leave a steady job, and a business to join the union when it’s really slow honestly scares me.. Maybe I have some blind spots where I’m not seeing things right, but hopefully I can get some insight here.