Start market research and building a web presence now! It usually takes two e-mails asking essentially the same question to get me thinking the answer is worthy of a post. In the past two days, I heard from a very an aspiring self publisher and a volunteer business consultant trying to advise a new self publisher about a timetable to use for business planning. I can understand the desire to lay out a plan on paper with milestones and a budget. Unfortunately, I can't offer any answers without the caveat "If you're successful."
If you're starting absolutely from scratch, no experience marketing, no platform to market from, no experience in book production, it's not going to be that useful to look at sales from a successful self publisher and assume you can get there your first year or two. I self published my first book in the mid-90's, and it went so badly I sold out to the trades. However, I never stopped working on my old website and started this site around six years ago for another self published book that was also a commercial failure. When I got finally going with the new approach to self publishing in 2002, I had the experience of a couple failures under my belt, plus two healthy websites. Every book I've published started life on the web, and with the last three books, I didn't make the decision to publish until I was literally getting e-mails asking when the book would be available.
Timetables are problematic for all publishers, but self publishers in particular. If you set goals and you don't achieve them, are you going to walk away? Don't laugh, I know publishers who have done just that, but I also know publishers who didn't see any significant sales for their new title until six months or longer after it was released. If you write a good book that doesn't go out of date overnight, there's plenty of time for word-of-mouth and the wisdom of crowds to begin lifting your sales. The work you have to do at the start to sell one book may translate into ten books sold just a year or two later. And that's why I recommend that you take your time and learn how to market your books.
If you try to take a shortcut, you may end up with expensive and meaningless sales. Aggressive promotion can sell some people anything, but if you're paying a marketing expert to force your book about fine woodwork down the throats of pensioners who can't hold a chisel, how likely do you really think it is they'll be recommending that book to their friends? Sales to people who don't really want your book and won't read and enjoy it can be bought and paid for, but you'd be better off spending the money giving away free copies to people who might really enjoy it.
As to setting a timetable for success, I'm on the record saying that self publishing as an act of financial desperation is a bad idea. It's a tough business, it takes most self publishers years to figure it out, and some never do. The only thing you can count on is that some of your assumptions will be wrong and others will be based on facts that change long before your business timeline runs its course. Planning is important, but preparation is more important, and the best preparation for self publishers is building a platform: a reputation, a recognized expertise that will help you sell books.