Do-it-yourself publishing
That's the kind of email I get directly or see on email lists and forums just about every week. I'm an enthusiastic user of InDesign but the last thing I'm going to do is tell such a potential publisher is to rush off to the Adobe web site and buy it.
The first thing I'll ask is: "Have you costed in the time and training (either personal or by means of reading and practising)?"
I'm all for such a person learning to use InDesign if he or she will take the time to learn to use it and, in the case of a book, will use it for many other tasks in future.
After many years of using Ventura, then PageMaker, I did not do a book in InDesign until I had worked on a number of smaller jobs to make sure that I could work efficiently in the program. It is a very powerful program, but that makes it very easy to do a bad job.
There is also the likely situation that a newcomer will get quoted a lot more for a layout job by a designer than an experienced publisher would be charged for the same work. The book layout jobs I take outside of our own books, I do only for experienced publishers and know that, most times, I will only have to do the job once, so can quote lower prices. As an extreme example, when I did tabloid newspaper layouts I quoted $20 a page for work from newspaper publishers -- and $100 a page for anyone else. Subsequently I just stopped doing the $100 a page jobs as they were not profitable, whereas the $20 a page was.
Yes, the would-be publisher should by all means buy InDesign but should also realize that this involves learning yet another skill. Do you have the time for that? In general the answer has to be "no" unless you can find a skilled person who is prepared to charge you on a basis that they are also teaching you to do the job. That designer will expect and deserve a high fee -- but it may be the cheapest long term solution for the publisher.

