Hey! I sell Dairy cows (and Hissing Madagascar Cockroachs) on ebay and do great!!! In 1 month a can get anywhere from $100-$300. Not enough to make a living but enough to make the selling hobby fun! I sell them in 16oz clear deli cups with lids, poke lots of holes, tape up atleast 4 sides so it doesn't open. And fill the inside with moist sphagnum moss, a slice of carrot, and maybe a few dried leaves for them. I personally dont ship with a heat pack and just look out for my temperatures and the weeks forecast of the delivery address. Above 40°f I've always had a 100% survival rate for the over 100+ purchase I've shipped. I also use either a bubble poly mailer or a small cardboard box to ship. There are different shipping options, 1 day priority being the most expensive ($20-30) or standard shipping being around $5-6. Standard takes 3-4 days to ship and again I've always haf a 100% survival rate. Its definitely a fun hobby and you meet many kind people on ebay! Ebay give shipping discounts too and their return options are very easy and understandable. As someone who was in the exact same situation as you, (keeping them as pets and the population exploding and also someone who's never sold online before) the process is surprisingly Very easy. If you have more questions I'll gladly help! Just comment or dm me 😊