I thought it was easy to become a SD resident? That doesn't sound easy!
It is MUCH easier to become a Nevada resident!! And cheaper too, although that would depend on the cost of your vehicle. Nevada has no taxes and most of the state has no inspections or emissions tests (Reno and Vegas do).
If you become a NV resident by age 60, at 65 you can stay in all state campgrounds for free after buying a $30 yearly permit. That's cheaper than New Mexico! But there are less Parks.
I've been with my mail forwarder in Pahrump NV for 6 years. Nobody is better!!! I'm sure yours are as good, they aren't better! She will deposit checks in by bank account at BofA! It was $100 a year for 5 years, this year she raised it to $120 a year. Find her here:
http://jbmailroom.com/
Here is the best reason to become a NV resident: it's NOT 1000 miles out of your way every 5 years!!! I spend 2/3 of my year within a few hundred miles of NV. In the winter at Quartzsite, I'm 2 hours away from the nearest NV DMV! It's closer than Phoenix! That's why I'm a NV resident!
Bob