This may have been answered, apologies if I repeat others before reading the whole thing...
If you do not intend to use the license commercially, there is almost no point it taking the course. Yes it is a good course, but you can get the same thing as just courses with the CG Auxiliary / Power Squadron, and likely other sources. You may get a slight ins discount, but would likely take 10 years or more to offset the Mariner's course costs. I highly encourage all boaters to educate themselves, but obtaining a USCG commercial license is not the most cost effective way, unless you intent to use that license. Full Disclosure, I do carry a 50T Master license, and while I don't use it full time, i do take on deliveries and training clients here and there. If I didn't I would have just followed the advice I gave.