If I have two websites, and therefore two ‘campaigns’, can I have one Google Adwords account, but pay for each with different bank accounts? I’m doing this for myself, not a third party, I realize that an sem company would just have it paid from one account and bill their clients. Do I need to have another Adwords account to accomplish this?
No - that simply isn’t possible. Billing is on an account level.
If the two websites are nothing whatsoever to do with each other, and the keywords you target are completely different, then you can have two separate accounts. That’s the only way to do that.