This topic comes up from time to time on this board. The outcome usually seems to be that although housekeeping at
DVC resorts is officially a non-tipped position, many DVC members like to tip anyway. And that's great.
However, if you look at some of the replies in this thread and in previous, similar threads, you might get the idea that it's common and customary to leave $5 on trash & towel day and $10-$20 at check-out. There was even someone who previously posted about tipping at check-out, based on $10
per day. (Given that there's no daily housekeeping unless you pay extra, I have difficulty understanding the logic of tipping on a "per day" basis at check-out.) I think such generous tips are the exception, not the rule.
My guess is that most DVC members don't tip housekeeping at all, or at least not on trash & towel day. Non-tippers and moderate tippers are much less likely to respond to a thread such as this than very generous tippers.
At a DVC resort, I typically leave a $5 bill for housekeeping on a master bedroom pillow on the morning that we check out. Sometimes more. I consider it a small "thank you" for the service they provide, not an obligation. No special envelopes are needed. Housekeepers know what to do with money on a bed pillow.
So, leave a tip for housekeeping if you wish, but don't feel that you're obligated to leave $5 on trash & towel day and $10-$20 on a full-cleaning day and at check-out.