Guest musicians

[Casey H]

Tried with non Taxi friends, but they aren't as dedicated.

100% this - they will flake on you, cause you to miss deadlines and not want to join a PRO or sign anything official.

+1
And sometimes not understanding general industry practices like co-writing means even splits, no haggling about percentages, etc. Or freaking out when they need to sign a contract, not understanding it.

[SubRivers]

I must admit this kind of given knowledge is a valuable thing with Taxi.
The probability of finding a quality musician that understands basic business practices in the industry is high here.