I think that taking group lessons at a local place is a good start. Your personal dog is reactive so Id offer to take a friends and offer to pay. Find a trainer you respect and explain that you’re trying to build your skill set. Maybe even take a few loaned dogs through some intro classes and see if opportunities arise to do an unpaid assistant trainer role or to do some fill in classes. Those group classes are an easy way to start building your exposure to different breeds and identifying common challenges that you see with owners.
Simultaneously, I’d work on developing one dog into more of a niche advanced sport. If nothing else, it will expose you to more serious competitors, more experienced trainers, etc. Finding someone willing to let you do this with their dog may take some brainstorming but if you’re paying and doing pick up/drop off, it’s a gift for the right family.
One person I know did something like this. She fostered heavily while developing a personal dog in obedience and agility. She met people, earned a reputation, and then started doing free puppy sitting for a few sport breeders who needed help in a pinch. Fast forward 10 years she makes $1k/week doing in house puppy raising with 1-2 dogs at a time developing foundation skills for sport work. People fly puppies out to her and they stay 4-12 weeks.
With a reactive dog, your in home options may not be viable but sharing that this is a path some take.
Much like horses, the vast majority of your trainers are going to make $35-50/hour but if you develop a deep knowledge and set of unique skills, the hourly rate can be quite impressive.