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Long tail or short tail is part of the story. What really matters are the searches + competition.
Use Google keywords tool (
https://adwords.google.com/select/KeywordToolExternal).
You should target keywords which have more than 2000 'broad' searches per month AND which have less than 50,000-60,000 'phrase' match results. (use the keyword you get from Google keyword tool and search for the keyword with quotation marks and look at the number of results).
Any keyword with searches below 2000 will not be profitable enough. And any keyword which has results in google above 60000-70000 will be too tough.
So it doesn't matter if it is a long tail or a short tail keyword. If the particular keyword meets the above criteria, then you should be ok. But that said, MOST of the short tail keywords do not meet the above criteria. They are gone now. They went like 10 years ago. So you will have to concentrate on long tail keywords.
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