As someone who has been in both positions (purchased a '16 new, and later a '16 used), if you're trying to be financially conscientious, used is the obvious choice. Realistically, a '16 or '17 with miles in the range you've stated should be around $30-$31k. ~$10k is a big chunk of depreciation you won't have to swallow, for what is essentially the same car but lightly used. I'd also say you should really hold out for a clean example with a good history, if waiting a little for 'the one' isn't in conflict with your goals.
As echoed in the comments here, this can be a very reliable platform, so with a good maintenance history and passing the eye test that it's been taken care of, there shouldn't be much cause for concern. When I bought my '16 R DSG with 30k miles, I performed the haldex service, and shortly after that the DSG service. Other than those two items, you pretty much just need to perform the regular oil/filter services.
Good luck!