I had a lot of PTO accumulated from years of FTE, mostly unused. Talked with my manager to get approval for starting a side business, then used the PTO to get 1-2 days a week to work on it (also with manager's approval of course). I did this for 4 months and by the time my PTO ran out I was ready to go for it and quit. The plan was, if after 2~3 months it doesn't start to get off the ground, rethink my plans and probably not quit.