Andrian, the highest paid artists in the world are Tattoo artists. A good tat artist should charge $100 an hour, minimum. If you are into art for just the money, switch industries immediately and start tracing stuff all the time! Of course, nobody can feel sane charging that much for RENDER time alone, that would be robbery. But consider how many hours you will actually put into it, and I would START at $100 an hour, and work backwards in negotiations. Render fees should also be considered, but think of those as "drying storage" fees, like one would with oils or somet other medium. Trying to explain rendering to certain clients might backfire, but you should earn SOMETHING for your downtime. Maybe $20 an hour or some such thing. Either way, make sure it's all up-front. And don't hesitate to charge outrageously, architectural work isn't cheap, and if they are a company they can probably afford to have it done right! Good luck!