I agree with Susan. You need to agree a list of exactly what tasks you need to do and how often. That way you can make a good estimate of how long it's going to take you and how much to charge - or even whether you have the time to do it.
Bear in mind that to start with, how long it takes YOU is likely to be longer than it takes the current owner, solely because they're into the routine and can probably do it on autopilot. When costing it out, you also need to take into account how long it'll take you to get there and back, plus travel costs like petrol or bus fare.
Off the top of my head, I can think of:
- Changing water & cleaning water bowls, x20, once every 2 days minimum.
- Spot cleaning. Ideally, you need to be checking for poop daily (I have morning and evening "Poop Patrol") but you could probably get away with doing it at the same time as the water changes, once every couple of days. x20.
- Full cleaning - as in emptying the tank, disposing of all substrate, disinfecting anything that will be re-used like hides and water bowls, replacing substrate. To do this properly can take me anything up to an hour per tank. This needs to be done pretty regularly, depending on how you manage to keep up with spot cleaning. Say once every 4-6 weeks? x20.
- Feeding - Depends what regime he has the snakes on and whether they eat in their living tanks or whether they have to be moved to feeding tanks. I suspect the former with 20 snakes. Usually once every couple of weeks for adults and probably just a matter of plonking the defrosted mouse in the tank and leaving. However, you need to take the mice out of the freezer in advance to thaw them properly. You might have to either make an extra trip there earlier on feeding day, or keep the mice in a freezer at your place and take the defrosted mice with you. x20.
- Checking setups. You'll need to do a quick check of the temps in the tanks with each spot-clean, just to make sure that heaters/thermostats are working properly. Usually not an issue, but all electrical equipment wears out and and breaks down eventually. x20.
You also need to agree a protocol for what to do if there's a problem. How does he treat problem sheds? Regurges - How does he want that dealt with? Health worries - Does he have a preferred vet? If they need to see a vet while he's out of town, can you just take them and have him sent the bill? Do you have his contact number so you can reach him at any time with concerns?
Critically, does he breed them? Would you be expected to deal with laying/recovering females, incubating eggs or hatchlings later in the year? That really would bump up the amount of time you'd need to devote to them.
Then there are the general issues like - if he has household insurance, will it affect that if he gives you a key to let yourself in? What if there's a break-in while he's gone, or things go missing? What's your liability or responsibility? Does he live alone or would you be dealing with other people in the house? How do they feel about having you in and out of there, potentially every other day?
It might sound like I'm being a bit alarmist here. After all, I have 18 snakes at the moment and I don't find them onerous to look after. However, going from 2 to 22 in one step (you'll still have your own to take care of) is a major hike and there are other aspects to consider.
You also ned to be absolutely sure that the snakes that you visit, don't have problems like mites that could be brought home to your own.
