Do you get several websites-Domains?
You can do that, of course. If it makes sense to keep the ventures separated, do so.
Can you have different websites that funnel thru one bigger account for accounting purposes?
I'm not sure I know what you're referring at. Is this about the merchant account? If so, you should talk with the merchant account provider about what's possible and permitted.
How do you know how many GB's or MB's you need.
This can be hard to estimate, especially when it comes to data transfer usage. You can generally estimate space usage simply by adding up the disk space that the scripts, database and the other files (images etc) use on your hard disk.
Is midphase good?
I've never used them myself, so instead of relaying hearsay, I will recommend you to do a search for their name over at webhostingtalk.com.
