Are materials purchased before or after rough inspections?

[Mike Kalob]

I'd like my lawyer to add a clause in the GC's contract stating ALL (or majority) materials (ie cabinets, stone countertops, vanity, appliances, flooring, ceiling) are to be purchased before rough inspections.. is this reasonable given below terms of 3 total payments below?

1st - 50% down payment to begin demo work

2nd payment - 25% after rough inspections 

3rd payment - 25% after completion.

My first contractor left mid-job post-pay; what's to stop this one from leaving after 75% of payments?   

If I change the 2nd line to "2nd payment - 25% after rough inspections PASSED and purchase and delivery of all (or majority) of materials completed," should this contractor leave again, at least I'd have the materials in hand to protect myself... That said, I'm not sure what the norm is, so want to be fair.

FYI I think this guy is actually good and means well, it's just the first GC's burn has me maybe overthinking things.  I understand there is currently a delay with materials, so I have to take that into consideration too. I want to keep this guy and want to be fair, but also don't want what happened previously to reoccur.  Advanced thanks.