If anyone has a full set of textured and animated RTS units,
I would like to use them for creating a demo-game.

I will not use the models anywhere else than for test-purposes
to realize this demo-game mission, or ingamevideo if the author wishes.
If the models are free, thats even better.

The set could be for example tanks, or Mechs for a futuristic looking RTS.

They should be low-poly, and not exeed 500 polys per unit.
They should also be skinned already, and have basic animations if
they have a "walk mode". Tanks or vehicles dont really need animation.

It should be around 5 to 8 different units, with various
main purposes.
For example: small attack vehicle, artillery, tank, ressource collector,
repair unit, unit-transporter.
Could also have Air-units, like a helicopter, glider etc.

The main purpose is to put them into my RTS test environment
during development.

here some Inspiration

http://ua.tauniverse.com/images/upload/wall_armlvl1_land.jpg
http://ua.tauniverse.com/?page=gallery&cat=5