In answer to your questions:
1. If you are looking to use multiple themes on a single website then the easiest way to manage them will be through a
WordPress multisite setup, so yes you may as well set it up this way from the start. Each theme could be in its own subdirectory:
e.g.
yourdomain.com <== Vantage
yourdomain.com/coupons <== Clipper
yourdomain.com/classifieds <== ClassiPress
yourdomain.com/jobs <== JobRoller
2. The themes don't automatically link users together, you'd have to share the user database but this can be done via the multisite setup
3. You'd ultimately need to edit each independently, but once it's not done it's not something you'd need to keep updating anyway..
4. Vantage has a built in .csv import tool, so you can use this to import bulk listings.
5. Clipper also has a .csv importer built into the theme
6. Yes, Clipper allows you to create coupon codes or printable coupons
7. JobRoller has Indeed integration built into the theme, however you can also purchase additional feed aggregator plugins from the
AppThemes marketplace.
8. Yes it can be done, an existing customer has done something similar with their Ideas site in the
AppThemes customer showcase
9. If you buy a single theme to start with, yes you can upgrade to AppThemes club at a later time paying the difference between prices at the time you upgrade.
If you wish to read more about individual theme features and check out the demo sites, you can get to these from our main
themes page. Thanks.