Then here is the tutorial to help you out: https://grabcad.com/tutorials/render-with-renderfarm-s
No, just a dollar for 1 RP. But most of rendering (product) almost come to 1.5 RP. As in tutorial you can image of cost of each render. On average it take $1.
1 RP costs $1 for 1 core in 1 hour.Compare that to the average workstation and you will see that is very expensive...
But I do have low PC, just a try on those renderfarms. But I don't want my PC to crash or smoke off. Anyway not going to pay, just using trail version given during registering.