Setting up and establishing an LLC is so easy, I don't recommend you do so until the tax year you will be "open for business". I know I set up my LLC in FL in about 10 minutes all on line.... and this was back in 2005.
Now if you have a valid reason to establish the LLC before year's end, then do so. As it stands now, I can only think of one valid reason off the top of my head.
If you "NEED" to open a business bank account now (which you probably don't) then the bank will require you to provide your business license from the state or county that issued it, in order for them to complete the process. So if you plan to open the business in 2020, and can wait until the end of Jan 2020 to open the business account, don't start the LLC process until Jan 2nd at the earliest.
Hopefully, you're not in California where they impose a gawd-awful high "franchising" fee in excess of $800 a year. Ridiculous!
