Code wise, you need a permit to do all kinds of things in your home. A kitchen or an addition – yeah you definitely need a permit because there is usually structural or electrical outlets/ plumbing being moved or entirely redone.
That said, I’ve seen a TON of home when we were looking that have additions done without permits. Some were clearly not done well. If you have the money, then hire a general contractor with a good rep, and he will handle pulling the permits. It will add cost, but it just is what it is. I’m not advocating either way, its ultimately what you are comfortable doing/ how much risk tolerance.
I don’t know what style your home is – craftsmen, spanish, etc? but if you want your home to be architecturally consistent or period, you should look for a GC that does a lot of work and can build /remodel to account for such.
If you have an old home and has NOT been updated specifically, and you are redoing a kitchen or bathroom, its a good time to have your contractor go through the plumbing and electrical and make sure its updated. You’re already ripping the entire damn thing out, you might as well make sure your plumbing/sewage isn’t going to fail on your beautiful new bathroom / kitchen. So while it costs more, I believe you will save in the long run + make an investment in your home if you plan to stay there.
With a kitchen, like I stated above, some contractors will want you to work with their cabinet vendor. Personally I like to have choice – because that means either I can shop for quality/design/have more choice but also that means I can ensure the pricing for things like cabinets are competitive. Because I negotiate in my day job, i’m pretty good at it, so I like to do my own negotiating when making large purchases. If you’re like me, you may need to find a GC who’s ok with this.
If you do opt to work directly with suppliers – have your GC order the product for you once you agree to terms/pricing if they will be the ones installing them. Whoever is doing the install of anything that requires specificity down to the inches should do the measurement and do the ordering.
If your kitchen remodel doesn’t mean reconfiguring your entire kitchen/walls, etc you can also consider IKEA…they have a range of cheap to more expensive materials. i know several people who’ve done really nice IKEA kitchen. they have a team who come out to measure your kitchen and work with you to customize. it was significantly cheaper than going the GC / custom cabinet route.