I installed a TVS50 with a 624 system and - apart from discovering midway through that I had a flakey 624 - had no major obstacles. I echo previous advise: buy from a supplier who'll back sale with tech support. You will have questions, believe me. I read the manuals cover to cover more than once, and can tell you that they don't hold all of the answers (at least not for my particular application).

Some observations on the TVS50:
Very powerful system with loads of features, most of which will go unused in the home environment. Because it is targeted for office use, it can be a bit clumsey to use in the home. For example, each mailbox must be assigned a PIN to prevent outside callers from accessing messages, as you'd expect; unfortunately, users must enter PIN when at home, too. You may find that you'll need to create documentation for your client for such common tasks as changing "outgoing message" presenting callers with mailbox selections. Handing the customer the fat Panasonic manual replete with all the features they'll never use probably won't cut it.

None of this is to say that the TVS50 isn't appropriate for home use, just that it may not be perfectly suited. On the other hand, I don't know of any "perfect" system.

One point others might expound on: depending on age of 1232 system, an updated firmware ROM may make for tighter integration with TVS50.