.

1. As long as the sites would be on the same server (host) any way, it should serve at the same rate.

2. As long as you follow the multi-site principles through out and keep all your custom modules/themes/files in "/sites/N-site.com" for each site , you should have no problem pulling them apart later.

In fact, as a general practice I develop all my sites on a local multi-site even though I will post them all to separate servers to be hosted as single sites.

Regards,
Michael Hofmockel
Drupal Expedition Guide
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Open Source | Open Access | Open Mind

If I was going to maintain a punch of sites on one server they would be in a multi-site. Code maintenance is the best reason to run sites off one code base (multi-site). Do it.

Reasons I would not do this for any particular site:
- The complexity of a site reaches a level that requires special consideration while upgrading.
- Traffic on a site grows to the point it deserves its own server.
- Site has sensitive data (credit card info, ...) with associated risks and liabilities.

Regards,
Michael Hofmockel
Drupal Expedition Guide
Switchback

Open Source | Open Access | Open Mind