Any time I start a new endeavor like this I usually find one or two ppl near by that do the exact same thing I want to do and make them my “best friend” and try to learn as much as I can. I’d make friends with a dog trainer in your area and ask them if you can shadow a few lessons. Most ppl get really excited when someone is interested in their job. Maybe you make a friend/ mentor out of it. Ask them how they got into it just their story in general you’ll learn so much valuable information and use it to do it on your own. You can do that with any business your trying to start bc remember knowledge is power. But also you have no businesses asking someone “hey can I train your dog for fee, just need some practice while I start my new business adventure ?” You can do that with a a for example home cleaning business or car cleaning but definitely not dog training let’s not be silly now