There is a great article on mobiForge called "A Guide to Mobile Emulators" which provides a great overview for how to test across multiple devices without owning them. There's also a good article entitled "Testing on Mobile Devices using Emulators" by Klaus Komenda.

From personal experience though nothing beats having physical devices. Speed of a device and navigation (fingers are much bigger than cursors) are really different between physical devices and emulated devices. If you're going to get into mobile seriously you will really need to invest in physical hardware.

yes, this is a very short entry :p