I left 121 for a medevac gig, then returned back to 121.
I flew for one of the larger King Air medevac companies in the country. Schedule was amazing, 7/7 with 12 hr shifts. Basically would sit around in a company paid apartment next to the airport and wait for a call. Medical benefits were 2nd to none. Pay is basically what it is, started around 60k and after 5 years it might be 67k/yr.
But the flying is tough. You will fly through all kinds of weather, at all times in the day/night. The airports will be everything from the busiest in the nation to unimproved with no taxiways. You will be responsible for weather, flight planning, fuel, weight and balance, pulling the plane out of the hangar, to storing and cleaning it. We were all single pilot, so you're responsible for it all.
You most likely won't fly in nice weather, as that is when the helos will take all the flights. When the weather goes bad is when the fixed wing start flying. Expect around 250hrs a year, give or take.