If you are going to do pre-purchase do it at a reputable shop that you plan on using once you've bought, there's tons recommended on here and don't do it at the dealer. RMP is highly recommended on here depending on where your located...actually regardless of where you're located go here lol
I personally wouldn't spend 21K on a 2007 335i only to put 40,000KMS on per year.
I would find a mint low KM E46 M3 and keep the acura to rack up miles on.
GL with finding something either way!