I get lots of Apple products from at least one of the majors, I even have an arrangement where they allow me to custom order the product, so that I get a higher configuration, for example iPhone Pro Max with 1Tb.
The stuff we don't keep for ourselves, I sell on eBay. Also try OfferUp. I've literally met people at the casino resort valet port cocheres to hand off goods to them for cash. The OfferUp people tend to be cheapskates, but at least you don't have to pay the 10% commission eBay snags from sales, and have to deal with shipping (unless you want to ship - OfferUp allows nationwide sales too for many categories of products).
Once you have sold to people on eBay, you may get in direct contact with them and sell directly - I have piranhas anxious to snap up whatever Apple goods I can get my hands on, albeit at slightly discounted prices because they have to re-sell.
One advantage to eBay is that buyers feel more comfortable buying because eBay offers a guaranteed "must be as described" policy - when it comes to especially iPhones there are a lot of carrier locked ones out there, that might be factory sealed in the boite but are essentially worthless without professional black hat unlocking.
You may PM me if your Apple stuff is high end, I'll buy it too. But to sell to me or anyone else directly via mail, you have to have some kind of payment system established that protects both buyer and seller, like PayPal, or a credit card processing merchant account.
You're wise to get only Apple goods - those hold value better, versus PC products that are essentially worthless after a few years of depreciation.