Learning as you go is what I did. I don't recommend it.
I bought a horse I was told was "perfect for a beginner". She was 7. I had done a little riding 30 years before, had recently retired from the US Air Force and thought I'd buy an experienced horse and learn to ride.
Let's just say there is a reason horse sellers have a bad reputation for honesty...
I rode her bitless because she wouldn't take a bit. She didn't buck, but she spooked a lot and seemed to be always testing me. A few months after I got her, she bolted while I was halfway thru the dismount, and I hurt my back bad enough that I had to give up jogging for 4 years (after 40 years). I continued to ride, but it hurt. She became halfway decent in a very controlled environment, but would regularly spin herself up to totally bonkers over nothing.
I finally quit riding her, took about 5 months of lessons, and spent months riding a ranch-trained gelding we also owned. Then I hired a professional trainer, who concluded Mia had either never been broken to ride, or had barely had any training and then been left in a corral for years. If I led her off property on a lead rope, she literally did not know to pick her feet up over a small rock - she would just stumble! By that time, she was pushing 11.
A couple of thousand dollars of training later, starting from scratch, the trainer got on her back for 5 minutes. The next day, I rode her with the trainer watching. A few months of twice weekly lessons for both of us, and I had a horse who would regularly jump sideways 6 feet a half dozen times on a trail ride...but who usually didn't bolt.
I've now owned her for 5 1/2 years. She hasn't tried to bolt in over a year. She hasn't jumped sideways for close to a year. I still have an unorthodox style of riding, though, meant to help me stay on and stay in control - because we USED to do a lot of spins, sideways jumps, and bolts.
In the last 6 months, my back is finally healed enough from Jan 2009's fall that I have been able to start jogging again (tough to start up at 55!) and also have enough flexibility in my lower back to start riding half-way decent. She isn't perfect, and she will NEVER be "perfect for a beginner". Our ability levels are slowly converging. In another year, we might be a very good match for each other...
So yes, it can work. But it has been expensive, both in cash and in pain. If I had to do it over again, I would not. I was in some ways lucky. The one incident I had with her hurt the soft tissue in my back bad enough for 4.5 years of pain, but she could have just as easily have fallen on my knee and crippled me, or dumped me in the desert rocks and broken my back. There is a sticky thread that deals with this situation: "Playing the Hero" -- when to 'stick with it' & when to realize it's time to move on.
In some ways, it made sense for Mia & I to stick it out. Underneath her fears, she is an exceptionally sweet and willing horse - and she has always seemed to like me. She came to fascinate me, and I think I needed that to get hooked on riding. But it also could have ended with me too crippled to ride. I've gained some wonderful experience, but I've also shelled out thousands of dollars, took more risk than I should have, picked up a lot of bad riding habits, and I still
don't have a horse I trust to go out riding solo in the desert!
You will have to make your own decision, and I hope God blesses whatever you decide - for both you and your horse. But I share this as a warning, because I know, from personal experience, that it can make a very rough road to travel.