We have been cleaning rugs and selling rug pad for 20 years. The standard rug pad has been Dura Hold but the problem is it breaks down after a period of time and is guaranteed for ten years (our experience is it breaks down after a few years but no one knows because it's under rugs and not seen). We recently found a new pad called Eco Supreme it is the same thickness of Dura Hold but the synthetic rubber will not break down as quickly and is water proof which will protect wood floors from pet accidents. We just started carrying it and will know more in a few more years after it is in real world use.
You need to buy the pad in bulk either 6'x60' or 12' x 60' so you need to have space and enough customer's that need pad. a 12'x60' roll is 385.00+ $75.00 shipping. They also have a thin rubber pad for people that only want to prevent rugs from sliding on floors.
Here's the source for the new pad gdhewitt@DSFCD.com
I think they are also called rug pad wizard, they carry other pads as well.
There are a few good reasons for rug pad;
Rugs last longer when there is cushion under them, it protects the knots from abrasion and cushions the fiber overall from impact.
They prevent rugs from sliding and slipping on smooth floors, preventing slips and falls
A moisture barrier prevents pet accidents form damaging the floor beneath the rug.
Rugs are more comfortable under foot when there is a pad underneath them
They help thin rugs lay flat, We have hot melt glued rugs to pad to keep them stretched and safe (with customers permission). You can heat up the glue to remove it and use solvents to get rid of it completely in the future if needed.