Is it acceptable to ask for course notes ahead of time?

I suppose there might be exceptions, but I think in general it is fine to ask. But explain your reasons as you have done above. On the other hand, don't expect that you will necessarily get anything back. Many people create the notes on the fly as needed, rather than in advance. That will depend on the course and the lecturer.

In my case I prepared a set of written notes that were printed and bound. Students purchased them for the cost of preparation. But I seldom had them available much before the start of the term as they were updated for each running of the class.

Often the class notes aren't a lot of use without the lectures they accompany, so you might not get as much out of them as you hope. The lecturer will probably not be happy with you if you also ask a long stream of questions about them prior to the course.

I doubt that many would consider it inappropriate or giving yourself an unfair advantage. Most would appreciate your enthusiasm.

I'd take a little bit different approach. Instead of asking for notes; just mention that you'd like some advice on how to better prepare for this course. Notes are notes and most of them don't make much sense until you've gone to the class. Same goes for PowerPoint slides; I don't remember ever seeing a set of slides that makes sense by themselves. The effectiveness of pre-reading notes, overall, is low.

Instead, consider asking for more explanatory resources such as a copy of last semester's syllabus (don't ask for the new one, 99% it's not been revised and you'll just stress the lecturer out), list of text books, etc. from which you can actually teach yourself some structures about the course or relevant skills before the class starts. And if the lecturer does make very comprehensive notes and offers to send along, even better.

As the others have already said, it is not unreasonable to ask (especially if the instructor is a reasonable person), but there are many reasonable reasons why the instructor could decline your request.

However, there is one issue that worries me: your sentence "giving myself an unfair advantage". Studying is about getting and applying knowledge, it should never ever be seen as a competition. This is just the wrong way to think about it. If you would read a book, would this also be unfair? Should students be banned from reading books? Should students not be allowed to ask their instructors questions because then they would know more than the other students? I hope you don't agree.

Thus, I would like to give you the advice to reconsider your image of studying. In the case that your university environment (friends, instructors) are unreasonable enough to also see university as a big competition, I would advise you to, if at all possible, change this environment. Eerything else is very unhealthy in the long term.