We would have to finance the purchase. Is that uncommon or unwise? Thanks!
Uncommon? Certainly not. Plenty of people do it every day.
Unwise? This may not be a popular opinion, but I would say usually yes.
It costs more--sometimes LOT more--to finance. But the more important thing is that, chances are, if you don't have the cash to buy your
DVC membership upfront, there's probably something better you could be doing with your money.
Do you have other debts that could be paid down? Do you have an emergency fund? Are your retirement savings on track? Do you have adequate college funds if needed? It's not nearly as much fun as DVC, but these things ideally should be squared away before you make a luxury purchase like a timeshare.
With that being said, say you weren't carrying any high-interest debt, and you had a little safety net in the bank. You're on track with your other savings goals, but you just don't happen to have an extra 15k laying around liquid.
In that case, say you bought and financed. You took a 15k loan on a 10 year term with 10% interest. Assuming you don't make extra payments, the interest on that loan is going to cost you just under $8,800.
With that, you need to ask yourself a couple of questions:
1.) Is having DVC now instead of waiting and saving up worth an extra $8,800?
2.) What else would you have done with that money? Is it worth giving up to make DVC payments?
Assuming that you're financially on track, the answer to those questions could be yes. Maybe you're willing to trim some of your discretionary expenses like going out, clothes shopping, or "toys" in order to accomodate paying extra for financing your DVC purchase. In that case, financing is not really a "bad" choice, just one of many choices you choose to make with your disposable income.
So, I guess the point of this really long answer

, is that if you're financing DVC, but you're doing it with disposable income (not money that really needs to be spent paying down your credit cards or beefing up your 401k) it's not the end of the world at all. But it's still always going to be cheaper to save up and pay cash.
Good luck with whatever you decide!