If you want to be a real professional gunsmith and do it for a living, NO correspondence course is going to do it.
If you want to get hired to work for someone else as a gunsmith, the correspondence courses are worthless.
No one is going to hire a mail-order gunsmith any more than they'd hire a Lamborghini car mechanic who learned by mail.
NOTHING is as good as attending a good gunsmithing school, AND taking the business courses if they offer them.
As I've said elsewhere, if you want to go into business for yourself, you'd better have a WAD of money to buy equipment, licenses, supplies, a building, and to hire an accountant.
You'll need insurance, and every Federal, State, and local license and permit ever issued, most of which you've never heard of.
Remember, you will NOT be a gunsmith.
You'll be a BUSINESS man who does gunsmithing. BIG difference.
You'll spend most of your LONG days doing business man functions like doing paper work for the government, talking to prospective customers, listening to disgruntled customers, ordering parts and supplies, doing the books, dealing with walk-in's including the mailman and UPS man, and somewhere in there, you'll get to do a little gunsmithing.
Last, remember that over 50% of all business's, no matter what they are or who's running them, simply go bust.
This is normal business attrition.
MOST gunsmith's that start out on their own right off the bat fail within one year for simple lack of paying customers.
Wanna be a pro gunsmith? Go to a good school, take the business courses, and about one year before you graduate start job hunting.
By the time you graduate you BETTER have at least one firm job offer.
Work for the other guy for a few years. Let HIM do the business man stuff while you put in 8 hours a day doing gunsmithing.
Save money and buy the equipment as you can, build up contacts in the industry, find out where your customer base will be, and what your speciality will be.
Then, if you really want to work 12 to 14 hours a day for what is usually less than minimum wage as a business man who gets to do some gunsmithing, you can go out on your own.
Just remember, you'll still be subject to that 50% new business failure rate.