Comprehensive Test Environment For Multisite

I’m wondering what is the best way to setup a live testing environment for multisite. Normally I would create a simple sub-domain on one my accounts, but in this case it won’t work because Multisite has to be a top level domain name. I don’t want to install locally, because I need to collaborate and get help from the others on entering data and transferring info.

Is it possible to get a temporary URL or what is the best work flow here?