I bet there’s plenty of sitters on THS that haven’t had any pets at all, especially those in apartments, and now they get to enjoy them, which I personally think is a beautiful thing.
You’ll have an amazing time if you decide to sit dogs too. Sticking to one small dog may be best for you until you’ve done a few, because even a well behaved dog takes a certain level of handling that you may not be used to, it’s the same for little dogs, but because they are lightweight they are much easier to handle.
Even if the dog you sit is well behaved, you can’t predict how other dogs will be with them, so you need to get used to passing signals down the lead/leash to reassure them everything is fine if they’re timid and that you are in control and there’s nothing to worry about.
Likewise if another dog has done something that has caused yours to react, you need to signal to them that they need to walk on and ignore the other dog. It’s in the way you hold the leader depending on the scenario, and dogs are more in-tune with your body language because to them, YOU are their world, whereas with cats, you are in their world.
Almost every dog you sit will form a firm bond with you as soon as you’ve walked or fed them. So what we do is, as soon as the owner has left, we don’t unpack our cases, instead we stick the kettle on and watch TV for 10-20 minutes so the dog has a normal calm activity going on so they’ll feel relaxed (and they’ll probably come and sit next to you), then we pop their leader/leash on and take them for a walk, you’ll be able to see how excited they get at the thought of you doing their favourite thing in the world with them. That seals the deal, they’ll love you from there onwards. They’ll show you where they prefer to walk.
Also, for us, we ALWAYS choose places that have grass, off-road walks, or very quiet country lanes that no one drives down within a few minutes walk of their home. You can sometimes tell from the owners profile images and description if their place is like that.
You’ll have a brilliant time if you try it.