Your art is great! The colours are vibrant and you've definitely got your own style going on. I've been doing pet portraits offline for years, but only recently started to offer them online. Offer a variety of options, like, pencil studies that they can download, or clean illustrations that you can mail out, for more middle of the road pricing, and of course, the big ticket portraits that take time. For the lower range, say, $99 and under, create a custom order and take the pay upfront. Anything more involved and expensive, take a deposit up front.
I don't charge much at all for my 8x10 custom sketches, which the customer downloads when finished, because I need to work on drawing studies daily and I don't normally get paid for it! As for big ticket items, like customized people portraits made out of plants or animals, I haven't had any takers online yet.
Start out with offering custom quick drawings first, to get a feel for the process. I found the online experience nerve wracking at first.
Anyway, best of luck!