Some professors have funny attitudes about what they could do with their grant money. As long as an experiment is sort of related to the general topic of the grant, they reason, it was fair game. When ordering supplies, the factor that determines which grant pays for it is whichever grant needs spent out, that is, whichever one is closest to ending.
In writing a grant proposal, they have little concern over investigating too closely whether a project is feasible. If it doesn’t work out the way they imagine it, they reason, they can always try a new approach, or “tweak” the aims. They have a much broader definition of the word “tweak” than most folks.
The lesson I was taught as a trainee was that funding agencies weren’t too particular about what was done with the money after it was awarded. One professor told me that funding agencies NEVER want their money back. That they will bend over backwards to work with you! When I got my own grants I discovered that funding agencies were not quite as willing to work with you as that, and not so keen about you “tweaking” the specific aims. (I’m a little bitter about that. Sure I learned the correct lesson thoroughly, but I would have learned it well the easy way. I suppose as a result of having learned it the hard way I am uber-respectful of funding agencies, I’ll track every penny, justify every expense and never have to worry about weathering an audit.)
When it comes to eligibility requirements on grants, these are guidelines rather than unbendable rules. Don’t try to hide something that might make you ineligible, but talk to the program officer before you dismiss a grant as one you are ineligible for. I’ve found that often, the guideline is a simple statement, but what they really want is more complex, and they’re willing to work with you if you fit what they really want. For example, one postdoctoral fellowship was for postdocs who had received their PhD less than 2 years ago, according to the eligibility requirements. But when I spoke to the program officer, the purpose of the fellowship was to encourage trainee scientists who were new to cancer research. At that point I had only been in cancer research for a year, so she reckoned I qualified.
But when it comes to allowable expenses, if you have any uncertainties at all, talk to the program officer before spending the money. It’s far too stressful to worry about what is going to happen if a grant can’t cover an expense, there are no other options to cover it, and the money has already been spent.