Ok so weeks before I left a large national to start up I had the following in place, this was almost 10 years ago now.
Car already signed up
Loads of stock
All of the tools, ladders etc
A years wages saved up in the bank as a backup
Loads of contacts potential customers I had met over the years
Accountant in place
Ltd company set up and ready to trade
Docket books, invoice books etc printed and ready to use.
I think it cost about £6k to put the above in place excluding the years wage I had saved up.
Then a lot of very long hours to get things up off the ground and running and finally never give up just keep going and trying.
And get approval ASAP.
Would I do it again, NO WAY.