Welcome to the insanity forum @Fidgety Spinner!
If you are planning to only have one wheel then yes, it is probable that after you "get your roll on" you will find that 30 km/h will seem frustratingly constrained. So aiming for a wheel that you won't outgrow as easily makes good sense... Having said that, everyone's "first wheel" tends to take a fair bit more abuse than their subsequent wheels - this is the natural result of the learning curve.
Some riders opt for a lower spec'd wheel to learn on, before then swapping up to a more serious wheel - either flicking off the learner wheel, or keeping it as a back-up (and so that you can teach others). Where budget doesn't allow for that, then the alternative is to work out the wheel you want / need long term and then ensure it is as protected as possible while you learn.
[start_sales_pitch] If you do go down the protection route, I sell the EUC Bodyguard, which provides excellent protection for both learning and beyond. Currently only for King Song wheels, but the range will be expanding soon. [end_sales_pitch]
Getting back to the question of what your wheel might be... If you are thinking about the Z10 level of wheel, then your other considerations would be the KS-18L or Gotway MSX. Any of these wheels will be more than enough to start with and then grow into. Each has their own pros and cons, so it is a matter of working out what is important to you. And these are the things likie trolley handles, lift sensors, weight, speed, et cetera. All minor in the bg picture, but some aspects are potentially significant for your unique requirements - For example, if you have to carry it up 5 flights of stairs, then you should know that the Z10 is exceptionally heavy.
On the Z10... If you have been investigating, you are probably aware that it handles quite differently to other wheels. This isn't necessarily a good thing or a bad thing, it is just different - and if you only have the one wheel, it won't make any difference at all.
The other big consideration is the availability of local support. Having that can be an awesome advantage (particularly if you aren't inclined to get your hands dirty). If you are inclined to do a bit of your own maintenance though, I wouldn't weight that too highly.
I hope that helps a bit (even though I don't think I said much). And do ask if you have any more questions... The more specific the better.