How to trade/sell on my website?

[hikatamika]

Tried searching for this one from a few angles ("sell", "shop", "PayPal")…

Anyone know how I can sell things or facilitate mail trades on my own website? Maybe with iFrames and PayPal? I think I've seen King Melon do something similar on his site.

Why?
I used to have a Ko-Fi shop, but I'd like to use it for specifically, like, supporter downloads or whatever.

I'd like to offer up original art for sale on my website in the future cause it's like, a cozy safe-space for me, and it feels more personable to have small things for sale on there than on a separated shop site.
Additionally I'd like to try and code stuff into my website "myself"(*) instead of paying monthly for Shopify or BigCartel or something. Paying such subs also makes me more hustley and grindy about marketing and selling. Having it be a slow-going thing on my site would allow me to be more relaxed and less stressed about it

Ideas that IDK how to Realize
1. Letting people choose multiple things from me to purchase (at once)… and then getting notified about it.

• Some sort of PayPal iFrame/API magic would be cool.
• Or instead, even serving up the visitor a mailTo determined by HTML form options they pick, or something, would work too. I could check inventory and manually have PayPal email a payable invoice back to the customer.

2. Taking intake for physical trade offers on my website.
It'd also be cool to solicit offers for trading things like original art cards on my site.

• I imagine this kind of thing would really benefit from starting off as some sort of mailTo, again with the prefilled content determined by what HTML form options they pick. That way I can discuss the trade offer with whoever wants to trade with me.

Passing the Mic
Anyone have any experience/insight on…

• PayPal iFrames & API
• HTML Forms that can shape/interact with mailTo links

…that could help me in these endeavors?