I've searched around here but could not find any booking system that would suit my need. I hope maybe you can help me out.

I've already seen question #11379 over here. Solutions provided there are not helping and scripts not interesting.

I'm looking for a booking system that support infinite number of hotels/rooms/pricingschemes.

There should be unlimited number of hotel owner/users, who can access control panel and set availability for their hotel. Or create seasonal prices and adjust them.

I should be able to have 15% booking fee paid through credit cart. I can work on integration with my system, it just needs to have correct APi/functionality to support this.

I love wordpress so if there are some nice plugins for that, I'm open for suggestions. But this is not a must.

It should be php/mysql based as I'm not good at anything else :)