The problem with the assertion that you should just know your budget or whatever, is this is a purchase with a potential 50 year outlook included. There is almost nothing in life that requires that level of future estimation. Even a mortgage generally tops out at 30, which is also an almost impossible amount of time to estimate. In the last five years alone, we had a second kid, moved out of the state we were living in away from two jobs we loved, because we were far from the rest of our family and wanted our kids to be closer to them. We got great jobs here of course, wouldn't have left if we didn't have that lined up, but the point is life happens. All the spreadsheets in the world can't account for it all.
With that in mind, you have to be pretty confident in wanting to visit Disney annually, or as they say AT least every other year. Or be comfortable renting out points or whatever. Then you have to be confident you have the financial cushion to cover your mortgage, car payments (if you have them), insurance, food, gas,
DVC, and whatever else if you lose your job. I would say most here, even those giving out advice on finances, don't have that all covered to a 6+ month level without borrowing from 401k or whatever.
I guess the point is, the financial analysis part is a little unrealistic. All you can realistically analyze is what you can do now, and maybe likely moves for the next five years, on an up to 50 year commitment. I am sure some of you will come back saying "well of COURSE I know my 50 year plan!" or something insane, but even if that's true I again don't believe that is true for an overwhelming number of people. So for DVC the biggest questions should just come down to, do you like the resort enough to pay a likely premium to stay there? Do you like Disney enough to return annually? Can you buy this without harming your families general financial well-being RIGHT NOW? Because it can and will all change. Kids get older and care less, or maybe care more. Grandkids come along, or one of you suffers a back injury that makes going around the park miserable. Again, spreadsheets won't cover it.