Firstly, I am not from US. I am very curious how much can I earn with YPN. I got around 600++ clicks per day with adsense and earning only around $100/day. Can I lease the ad space to other YPN account holder?
I think you should be able to. As someone else said, you are just leasing space. But, wouldn't it be better if you just displayed your own ads and kept all the money? If you lease out the space for someone putting YPN ads, you won't be making as much money imo. YPN typically pays less than Adsense (based on publishers' experiences) so even if this advertiser gives you all his revenue, you will still get less money than you would by placing your own ads. Just some food for thought ..... Unless, of course you can't place Adsense ads any more for some reason. Have you been banned??
I personally only use Adsense, but that's what I have heard from other webmasters. They say that sometimes pay per click might be higher but CTR is quite low due to poor targetting. Google shows much more targeted ads. Again, this is just what I have heard from other webmasters.