how long is a piece of string ??
your going to get about as good of an answer for that one
too many factors to plug in to give you even a guess at an amount
if it's solo, I'd not waste my time unless you already have a market for it. I wouldn't start shooting anything that wasn't pretty niched in focus. Go onto c4s and find the hottest niche that is turning up new videos every day, and start there.
I'd probably make sure I was shooting 4k also, if your trying to sell this to other paysites, your not going to have much luck with 1080, since they all want 4k now
Good luck
