Many of those homeowners who are in forclosure will not have paid off their timeshares. Depending on how the sales contracts were written, it might not be so bad for the HOAs (though the HOA is who will get hurt if the timeshare IS paid off).
For all those folks who financed their timeshares, they are making monthly payments to the developers. They owe much more to the developers than to the HOAs, and the developers probably have terms that will allow them to forclose sooner than the HOA. Thus the developer takes title to the unit, and the developer is responsible for the annual fees - not such a big problem for the HOA, except that the developer is back to having a bigger stake in the property.
If the HOA forcloses, the developer no longer has the unit to sell again - the HOA does. And the HOA can afford to sell the unit for the prevailing true market value, because all they have to absorb is the back maintenance fees - not the $20,000 that was still owed on the loan.
As for the OPs original question, I would expect the minimum income to go up, but no credit score requirement. Few people are going to be willing to let the developers check their credit until AFTER the tour (when they make their mistake and buy). Of course, I don't recall them ever checking our income, other than what was stated, and don't know how they would go about doing that either, without express permission.
We have been on 2 local tours in the last month, one to a resport we stayed at 5 years ago (and toured then too). We have noticed some differences in the way they are selling - pushing the value of owning a local timeshare, not pushing the idea of trading nearly as much. The tour we went on this weekend, the salesman was clear about the ability to trade for anything "available" and noted that listing in the book don't mean the units are available. Vacation Village was offering their "gold card" as part of their "first day" incentives, and indicated that your children would be eligible for their own gold cards when they turn 18 - this allows access to the amenities year round, not just during usage. Of course, if you can find a resale of one of their original units, you might have similar usage written into the sales contract - now they "sell" that as a separate bonus.
We did meet a man at "Oak & Spruce" who owns one unit there, and always trades it, because he lives 20 minutes away. He figured his annual fees were less than membership in the YMCA, and he gets similar benefits through using the amenities on a pretty much daily basis. If there was a resort with decent amenities that close to our home, we might consider such a purchase too. The sales offices know this, and maybe we'll see more of them market the resorts along those lines - local use, plus an annual vacation thrown in.