I run a small custom forage operation, more of a sideline than anything. I cut with a JD 6710, 15 foot corn head, 10 foot hay head. Also have 4 16 foot boxes. You will tie up a lot of money fast if you want to play that game. No one will want to be the first to cut, but when you start everyone is calling. Cutters are not cheap and are very high maintance, parts are not readily stocked around me so you quickly get used to over night or next day charges. You have to get good iron to do custom, doesn't have to be the newest though. Boxes or trucks need to be top notch, you don't want to be wrenching on those when you are cutting, besides the cutter will give you enough grief. Then you get the people who want theirs cut right away, but don't pay. I've only once never collected cash, but was able to do some fly by night repo, so I've been lucky.
If you were in my area, I would be glad to sell out to you, not because it is that bad, but is becoming more of a time issue for me.
Hope I did not discourage you, best of luck!