Welcome to the community.
Horses or dogs would be a major commitment for 12-20+ years are the life span of those animals. They would be a commitment of lots of money and time. Ways to help in those areas you could volunteer at pet shelters and rescues.
Learning about caring for a fish tank and it's inhabitants is a wonderful hobby. There is always something new to learn and after you know about caring for the aquatic critters, you can help other people learn about their aqua pets.
Fish and tank keeping has been helpful to people who have experienced traumatic issues, PTSD and related things.
This is a KEY and very important cache of information! When you understand the basics it does allow fish keeping to be more enjoyable. The local pet store employees do not always know much about actually keeping fish.
The biggest thing is that you have a cycled tank which means good bacteria grow in the filter media and in the aquarium which will process ammonia from old fish foods and poo which are toxic to fish and change them to not toxic materials to help keep the tank safe for the living creatures inside. Its called nitrification cycle or cycling a tank.
Guide to Starting a Freshwater Aquarium - Aquarium Advice
You might want to start with something like an inexpensive 10G tank (Petco might be having their dollar per gallon sale)
get a good filter like an aquaclear 30 or 30- 50 (which could be used in a bigger tank later) and get a Betta.
A Betta male needs to be kept as the only Betta fish. They usually enjoy interaction about their person coming to feed them, and are beautiful. After you decide that you enjoy keeping a fish you could branch out to a bigger tank and community fish or whatever you'd like.
By starting slowly and not a bunch of fish with different needs, you can really focus on the care of your tank and fish and get in some good experience.
Knowledge helps you be successful. Reading and learning about other types of fish can help you figure out which fish you want to keep. If you don't want to start with a Betta, it can help you build a good tank and stock list.
A great way to start /help decide what fish you enjoy is visit a good local fish store, ideally a locally owned one. Watch the fish in the tanks and see what draws you back again and again. Patience deciding what seems to be the most interesting to you is the beginning.
By knowing what fish you want to keep you learn what kind of tank, water conditions, tank mates, substrate, plants/cover, etc. they need and build the tank around them.