No, a vet won't check for a UTI in the general course of a routine annual check, unless you mention something that would indicate he might have such an infection. Certainly it is worth getting checked anyway.
As to the breeding thing - I think you made it fairly clear that that isn't one of your aims in life.
However, I will take this opportunity to let you know
why Boxerworld (which, incidentally, will not be changing it's name anytime soon

) takes the stance it does on responsible breeding practices only.
The boxer breed suffers from a number of genetically inheritable defects. They're not minor ones - primarily we're talking about hip dysplasia and two major heart conditions (boxer cardiomyopathy and aortic stenosis). Those conditions will have a major impact on the quality and length of life of any affected individuals. Unfortunately for the breeding fraternity, those conditions may not be evident until a dog is 5 or 6 or more years old. Remember these are genetically inherited conditions - so if you breed an affected dog then it's offspring are likely to be affected too, and so it goes on.
Not surprisingly, the problem (that is, the incidence of affected animals) has been getting steadily worse over the years. Nobody breeding boxers could credibly claim that those problems don't exist in their lines. So what's the future for the breed? Let the incidence of serious health problems continue to grow unchecked until that's just what you get in a boxer? A life expectancy of 2-6 years? No - I don't think any of us want that future for this breed.
The alternative is to spend the money on screening for those conditions before you breed. It still isn't 100% foolproof - but it is a heck of a lot better than continuing with indiscriminate breeding practices that are slowly (actually, not that slowly at all) and surely destroying this breed.
And frankly, it isn't
that expensive either. Sure, it probably means you won't make a profit from breeding your dogs just one time - but everyone claims that isn't the reason they breed anyway...
So health considerations are the primary pre-requisite for breeding dogs. If you aren't prepared to do the testing, or aren't even aware of the problems you need to be screening out of the breed of dog you're breeding - you've no right at all to be doing it. That is the single biggest problem with backyard breeders (and with show breeders too, if they don't health test - and some still don't). They're not necessarily bad people and many of them love their dogs like children. But whether it is inadvertant or not, their ignorance is destroying the health of this breed. You can call that an Aryan attitude if you like, but before you do, just check out the health section here for the hundreds of heartbreaking stories people are posting where their dog has died suddenly, has a serious heart problem, has mange, can't walk because of dysplastic hips at only 2 years of age... the list goes on. And it is *avoidable* if only people would take breeding with the seriousness it deserves.
We humans created this breed, and every person who ever breeds two dogs together is responsible for the outcome of that breeding. To knowingly breed two individuals affected by a genetic disorder together would be akin to criminal. To do the same thing "unknowingly" because of ignorance or being unwilling to spend the money to screen for those disorders is no better.
So this website will continue to promote responsible breeding practices *only*. We will not welcome or condone backyard breeding practices here, and will continue to try to educate new members on the subject. It is unfortunate if you're so offended by the advice people have given you here - maybe some people could usefully emply a little more finesse in giving such advice. I hope you'll take it on board all the same though - style of delivery doesn't affect the validity of the content

. But more importantly - there are others who will read this thread, who won't be taking that advice as a personal attack. If that means just one person who stops, does a little research and either spays/neuters their pet instead of using it as a breeding machine, or who proceeds but only does so *after* health screening, then far greater good than harm was done.
A couple of useful links for you:
http://www.boxerworld.com/forums/showthread.php?t=59482
www.boxerworld.com/breeders