Well, unfortunately it would be a first level start. I'm big on the classic approach. Given that it is the start of a campaign that if it takes off I can see going on towards epic levels I like to see the initial fear of a party kill looming around every corner. As for books and classes, none of the books I can think of are off limits. I'd even allow the use of psionics despite my lack of love for the idea or the book itself. Of course, I'd expect nothing on the level of a demi-god (I think complete divine) provides something along those lines. But if something comes up as an issue it would be addressed at the time. As for house rules, I've never really had any on the table. But given the medium we are using here my only "house rule" would most likely be that the dice rolling would be really left to a minimum because I'd prefer the creative side of things not be hindered by too much. For example, rolling might certainly be necessary for fighting. But if I see that your sleight of hand is being modified by a positive eight as a DM I wouldn't take a second glance as someone writing in that they snatched something off a table near someone who might otherwise stop them from stealing something. 

As for the pathfinder rules I certainly will take a look at it. I have a couple of friends who play pathfinder on the table top but I've never had the inclination to explore it. Perhaps now I will.