Some big considerations (and there are many missing from this list):
Business plan - Unless you for some reason already have a nice little nest egg, you'll need a thorough, realistic business plan in order to earn the loan money necessary for opening a practice.
Market research - Know the area you hope to open in. If there isn't a need for an audiologist in your area, either because there are already several practices or the patient population just isn't there, you're going to struggle.
Really, really consider the cost of your overhead and how it stacks up to a realistic expectation of gross income during the first couple years. You need to think of everything, as even several little missed costs can add up quickly. Office rent, utilities, staff wages/salaries, office supplies, shipping costs, etc. (and that's a big et cetera). Also, don't forget about...
Marketing - Everyone in your area is familiar with what's available to them, so you need to get your name out there. First impressions are important, so decide if you'll be the audiologist who values the services you provide and respects the integrity of the profession...or if you'll be the one offering a free Butterball turkey with every hearing test, or worse...free audios. Newspaper ads, a website, mail-outs, etc. all get your name out there, but word of mouth is the strongest marketing force for a local practice. The better you treat your patients and the more you outwardly valuate your profession, the more likely patients will recommend you to their friends.
Expect a slow start. It is not at all uncommon for private practices to operate on a net loss for the first year or so. If you manage to earn a profit early on, good on you...but have an understanding of when things become stagnant or regress and have a plan on how to curb your losses.
As the prior poster mentioned, it can be easier to buy out a previously established practice, though this also comes with a handful of important considerations. Opening or taking over a business comes with many, many risks, but can turn out to be very lucrative if done correctly.
If you're interested in private practice work, I'd recommend that you do your research, not simply in the area of audiology practice, but in general small business management and healthcare provision. An unexpected surprise could sink you whereas some prior earned knowledge could keep you afloat. As a starting off point, I'd recommend finding the chapter in the Katz book regarding practice management. It does a great job of covering the basics.
If you take that road, best of luck!
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As an afterthought, maybe stay away from the many buying groups out there (i.e. Audigy). They offer to handle the business aspect of your practice while you handle the clinical work, but this simply means that you lose some of your autonomy. While these groups may not be particularly toxic to the private practice audiologist, I would just about guarantee you that taking the time to build up a solid understanding of business practice as well as having the patience to handle such work on your own would benefit you immensely in the long run.
