Mistakes are good for those who learn from them but there is no logical explanation why you would choose to go through a long expensive and time consuming learning path filled with mistakes and 'lessons' when you can just learn as you go from an experienced individual who can help you reduce that path and minimize errors.

When I was launching my first startup, I reached out to a few connections of mine, including Craig (from Craigslist) and Aaron (CEO of Jobing.com) - it was them two whom I worked with shortly and still failed that startup. It wasn't that the idea failed, but I learned so much on different perspectives that I completely abandoned what I had to refocus and launch a completely different business. Sold that business a few years later.

When you reach to mentors however, it's important for you to consider their history, their connections, their level of involvement and the closeness to your own business model - have they launched something similar? do they own a business which you can partner with once you have built a relationship with this mentor and built a good product?
Also, don't go with hard headed individuals who think they know best - no one knows best, what they are supposed to bring to the table is an experienced different perspective on the same situation you are going through now that they have gone through themselves - give you their perspective, introduce you to the right people, give advice and let you make your own decision with all things considered.

I have a friend who launched a very innovative mobile app, I think it could be huge if well played, but due to them having influence from so many 'mentors' they screwed up their own growth and now the guys are doing 'marketing' to try to get revenue - not realizing that in it self is a business that distracts from the long term.
My name is Humberto Valle, I'm the founder of Unthink, a digital marketing agency that is now globally known as the most helpful. If you would like to get in touch or need anything related to marketing please visit us at www.unthink.me.