A: It can. But it can also help. The answer is not clear cut. It depends on when and how you do it.
Q: How can publishing an ebook help me get a "real" publisher later?
A: If the ebook is a smash hit, a big publisher may well come to you with an offer to produce and market a paperback. Or an agent might show interest in representing you.
As they say, nothing succeeds like success. This has happened before and will happen again, especially as ebooks increase their share of book revenue even further. (In 2012, 25 of the top 100 ebooks sold on Amazon.com were published by indie presses.)
Good book reviews, interviews and press about a recently published book can also get you visibility, supporters - and even fans. It can be a positive step in your path as a writer.
But for that, of course, the book must be very good.
Q: And if it's not?
A: Publishing a bad book can hurt you.
If you publish too early, before the manuscript is really ready, or a book that is full of typos, that can discredit you.
No matter who publishes you book, it's important that your manuscript be properly edited and professionally presented, with a great cover
Also, some agents say they are reluctant to represent a book that has already been self-published. But when you talk to agents, it turns out that often really mean is a book that is self-published with few sales.
Q: What if what I really want is an agent?
A: If what you really want is to be published through traditional channels, then you might want to focus all your efforts on getting an agent. That means, query letter, proposal and a willingness to accept rejection.
Think hard about what you want and what will satisfy you.
Publishing an ebook is very easy these days. And there are many success stories. But most ebooks have modest sales. And are unlikely to be picked up by an agent or a big publisher later...