I don't know if its already been said, but perhaps the #1 beginner mistake is listening to and accepting advice from people who shouldn't be giving it because they are very new and/or have very little personal experience or verifiable knowledge of the topic....especially when they are attempting to sell you something
Not to mention ignoring advice from people that clearly have more knowledge and experience then you in favor of your own desires and unfounded personal opinions without honestly and responsibly considering/evaluating their points and your own motivations for wanting to do something anyways.
I'm not saying the words of such people should be law but before you go against them you should have very valid and logical reasons not to mention contingency plans if things go wrong to limit the risks. IMO
