...for under $700. (Laptop)
The store ads have mostly PC's with Vista premium for $560-$650, but not Business. What's the least expensive way to get it? Ordering a custom PC is more expensive and I don't want to wait 2 weeks.

I could upgrade from Basic, but I'd need more memory too. Can any new PC handle the upgrade?
Can you upgrade from Premium?...Is that a good idea?

Is Vista Business worth the hassle I'm going through? ,...The "Scan + Fax" feature in 'Business' sounds good: Can Premium do that to, without hassle?

I personally would not buy Vista at all for a while, until some of the bugs are worked out.

That's another issue that's bugging me. But I need a new PC and they all come with Vista. I was thinking: if Vista gives me problems, I'd put XP on it and when the bugs are worked out I'd switch over.

Try Newegg.com They have a few preloaded with Vista Business. They even have some with XP Pro installed.