Decide how much money you can afford to lose. There is a chance that putting on the first festival (and perhaps the first few festivals) will be functionally equivalent to filling a shopping bag with currency and burning it.

Now decide if you love your concept festival enough to do it purely for love.

Set realistic goals/expectations about attendance. This is VERY HARD. Even those who style themselves the most hard-headed of realists are easily overcome by wishful thinking here. You cannot be TOO pessimistic when doing this.

Prepare for the LONG haul.

Festival do not develop a "critical mass" of attendees immediately. Clifftop comes to mind here. There's intense competition for people's time and discretionary income. Your potential attendees live very busy lives with full calendars. It might be a while before all the people who "should" be attending your festival actually show up. I can name 10 festivals off the top of my head that I'd attend if I had the free time.

Russ (been there, done that)