I've got a couple E-Tes units. I have been asked by a local rental company in the past if I would rent some equipment to them to rent to other clients(dehus, air movers, etes). Here are a couple things to consider (by the way, I did not do it)
According to my insurance coverage, I am the owner of the unit and if it malfunctions and damages something (or hurts someone), you are still responsible.
The people have no or limited training...and you can still be responsible for damages or injury.
The people using the equipment usually have no training and damage the equipment (and can cause damage to other property and or injury to others)
You might also be just competing against yourself in some cases.
In the end, it was a very bad deal for me.
Mark
Saiger