For instance, should I base it on a dollar amount per hour I work on the project, either as a PM or as a guy who actually puts on the tool belt?  

Or, are we more of a thorn in their side until we have a few more deals under our belt?

I suspect after you have a few under your belt you'll find that you're able to be more flexible.

It isn't practical to find "affordable" GCs, at least we've not been able to in our rust belt market, where home prices are way below national average.

I plan on getting licenced during some downtime from school just to have it under my belt.

You should be looking for a light rehab project that you can finish up quick and get some experience under your belt so that you can get better terms for those more aggressive projects.

If I sign up for Karate lessons I'd like the dude teaching me to be a black belt.

Got to get your first deal under your belt.

The plan is to get that under my belt then continue to build aggressively.

If you are someone with a few properties under your belt seeking for more real estate specific knowledge some of the books on bigger pockets might be a more economical way to obtain real estate specific knowledge.