John le Carre was in the Security Services before he started writing spy novels. Andy McNab was in the SAS before he started his career as an action novel writer. Emma McLaughlin and Nicola Kraus, who wrote The Nanny Diaries, both used to be nannies.
There are lots of examples of authors working extensively in a particular field before starting to write novels that draw on the experience they gained in their course of their work. Equally, however, there are plenty more examples of authors who have never worked a day in the kind of work their characters do – and yet they still manage to make great careers out of their writing.
So this raises the question: is it necessary to do practical, hands-on research for your novel?
In most cases, I would say probably not, if only because it’s not always very practical. After all, if you’re writing about a character with multiple postgraduate degrees who works as a brain surgeon/rocket scientist/world-renowned academic or similar, there’s very little chance that working in the field is going to happen for you (unless, of course, it just so happens to be your current/former career, in which case, hurrah!). However, getting a feel for different jobs or environments can be useful for novels, and so a bit of work shadowing or even just talking to people who work in the industry can be useful to get a grounding in subjects that are necessary for your book.
Researching novels can also be a great way to have a go at things you’ve always wanted to try, and a bit of real life knowledge can go a long way, so it certainly can have its benefits to get involved in practical research.
How much research you ultimately do will depend on what kind of writer you are. Some people like to have a thorough understanding of something before attempting to write about it, and that will naturally lead to much more research than if you prefer just to get straight into things. On reflection, in some cases it’s probably much better if you don’t do any practical research before starting to write your book.
If you’re writing about a serial killer, for example… That could be awkward.