I've had dachsies all my life - standards and mini smooths. I adore them, but they are hard work, and they're looooong lived (17-18 years average - I had one live to 20) so you really need to happy being glued to a stubborn little dictator for a long time.
Utter buggers to house train - of the seven or eight I've had only two have been 100% clean. They just don't see the point. For this reason, they're tough to have with DCs around - you never know when a bomb has been dropped somewhere and a blissfully unaware child will go gambolling through it.
They're notorious coprophagics. If you don't know what this means, Google's over that way -->
They can be very highly-strung, and tend to only bond with immediate family. My current two are the most sociable I've had. Most of my others have been lovely with us, but nippy yappy little shits with everybody else, despite avid socialisation from puppyhood. Only one, maybe two, of the dachsies I've had would have been good therapy dogs - the one who would have been great (I even took him on placement with me as a student occupational therapist) had a bit of terrier in him which I think helped his temperament somewhat. He was also one of my only completely housebroken ones (and the one who lived until 20 - beautiful boy!). Overall, I think you'd need to have a dachsie first, then decide later if they'd make a good PAT dog, not get one with the intention of turning them into one as they may well not agree with you!
Two of my dachsies have needed back surgery, so insurance is a must. Those of you who let your dachsies do stairs and jump on/off sofas - please, please, please don't. Just because they can, doesn't mean they should. The stair gates I have are to stop my dogs attempting the stairs, as much as they are for my DCs.
Most of mine have been so epically lazy, or so antisocial, that daily walks were entirely optional. Access to a back garden has been all any of my dogs have ever needed. My current girl dachsie hides if she sees her lead being brought out then pretends she's paralysed if expected to then walk. Suffice it to say she was dead easy to keep on crate rest after her back op. 