I think Joe pretty well covered that one, but let me add a couple of thoughts.

If you have a welding business with insurance, licenses, bonding, etc, never work outside your coverage.  Contractors licenses generally state the range of things you can do and still be within your licensure.  Insurance will also be rather particular as to certain non covered items.  Joe mentioned hitches.  Most shops will find their liability does not cover the manufacturing and installation of hitches.  If you buy hitches from a reputable hitch manufacturer you can bolt it on in it's proper application then there will be no problem.  Don't build it yourself or modify it.  Public safety issue and you are not an engineer. 

Along with that, if you are a business especially, don't work outside your welding qualifications.  If something goes wrong, your insurance and the customer's lawyers will eat you alive.  If you aren't qualified for the job requested be very careful.  There are things that are not code critical, I am not referring to those (fences, railings, light equipment repair).  But if you don't do heavy equipment repair properly, don't do structural properly, don't do piping properly, with all the right code qualifications you can lose everything and possibly cause injury or death.  Not worth the risk. Even some railing can be rather critical in certain applications.  I would not let just anyone build some of the ones we have done.

Know your customer.  Especially today.  Many people want something for nothing.  They also love to sue.  And the courts are very unstable.

And lastly, don't do a job your equipment won't handle properly.  Example: welding heavy machinery repairs on steel over 3/8" with a 110v innershield wire welder.  You won't get the needed weld.  Or: weld cast iron parts with a GMAW short arc.  Unless it is only decorative.

Make sure you and your equipment are right for the job.  Then, do whatever needs to be done to feed your family and know you have provided professional, quality, competent service to your customer and the community.

Have a Great Day,  Brent

A car or truck wheel. My old shop was right in downtown Nashville and I got tons of guys bringing cheap cast rims that would crack and couldnt hold air. I also heard a story about a "jack of all trades" type that got killed trying to weld some cracks on a wheel with the tire still on it that had fix-a-flat in it.

Darren,

You must work in a different environment than I do...

When we keep the suits happy... We get what we want when it comes time for new equipment or a raise!

Yes sir, Yes sir, three bags full...

One may fix little widgets for the suits and still mantain integrity.

I try to say yes to the folks who can say "yes" when I need something.