First off, Welcome to the community! Now, onto your question.
You can either estimate (if you’re on a coast it’s going to cost you more to ship than someone in the middle of the country) or just add the cost of shipping to the cost of the animal and list it as having free shipping. As a heads up, depending on where/when you’re shipping and the size of the snake, you’re going to be using bigger boxes. 7"x7"x6" is the minimum size I use (I breed corn snakes), and if you need to ship somewhere using a heat pack, that requires a minimum 12"x9"x7"
Shipping supplies are going to be another thing you need to worry about. Are you going to be doing enough sales to keep them on hand, or will you order as needed? You can get an idea of pricing on SYR for bulk supplies or individual kits. That will also factor into the shipping or animal price in the end.
As for where to ship, for the safety of the animals the best bet is always going to be a ship center. It has to be one that accepts dangerous goods, meaning no deliveries to Fedex at Walgreens/Dollar general or Office Print & Ship places. You will also need to either schedule pickups or ideally drop them off at a ship center (same rules as delivery) as well. If you feel comfortable about shipping to homes, then you can do that, but it means that animal will be on a truck for an indeterminate amount of time, with more possible hazards.
One thing a lot of people don’t do but I heavily recommend for small hobbyists especially, is using one of the shippers who offers on time/live arrival insurance. It will make shipments cost more, but it’s a good fallback in case of delay or in the worst case, death of an animal in shipment. I’m not sure of Redline’s pricing, but SYR charges $2.50 per $100 of coverage. Always insure the full value of the shipment including the animal, not just what it costs to send.
One last tip: Always pay attention to days of the week, weather, and heavy shipping periods. I only ship Tuesday/Wednesday for Wednesday/Thursday arrival for safety. Mondays tend to be busy days, Thursdays cut it a bit close if there’s any sort of delay, and you absolutely never ship on Friday because those shipments will not arrive on time. Weather is always checking your local weather and the destination local weather, and working around any sort of severe storms or temperature issues. I go one further and check the weather near the hub the animal will be traveling through, just in case (either Memphis or Indianapolis). Shipping periods are the other piece of the puzzle, and while you can’t predict them all, the good ones to avoid are around holidays or busy online shopping days. I don’t necessarily ship the week after Black Friday, or from about December 15th - January 15th.