Warnings on resource usage

[Nutter]

I know that y'all will drop sites that have the possibility of bringing servers down due to excess resource usage.

Is it possible to get a warning when a site gets close to this limit? Or, is there a way to see that site X is using y percentage of the resources on its server? Or, at least an email saying that "we're shutting down your site tomorrow if you don't fix it."?

Also, I'm on a reseller account and have several domains hosted under it; all of them mine. Would one domain being booted affect the others on my reseller account?

Here's why I'm asking: I am working on a project that will be fairly database intensive, but with few users. It will have the ability to be taken off line where the users cannot log in so that I can work on the databases or limit access in case I go over my resource allocation. My problem is that the resource limit is an unknown to me.

Or, do you have an estimate of how many users can use a PHP / MySQL based site without causing problems?

Ultimately if this project is successful I"m going to move it to a dedicated server anyway, but I want to make sure I don't hit any snags while getting it built up.

Thanks,
- Ryan