I'd suggest starting out with a column here, since it gives you ready access to a large pool of questions. If you're good enough, you could eventually move off to a stand-alone webpage; you'd need to have built up your own fan base, of course.
As for starting your own webpage; I could write a BOOK about that. But for now, I'll just say that if you're serious about it, I strongly recommend getting your own domain and having your site hosted by a professional company, not one of those free-site services. You should be able to get decent service for $100-$200 a year.
But ultimately, the most important thing is to get really good at giving advice. One key factor is to write clearly, quickly, and well. Good grammar, punctuation, and spelling help a lot.
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