Two years of ground work?
First of all, I don't lunge horses for more than a couple of days, and only if they are old enough to back. Senseless lunging is very hard on a young horse's leg joints.
I ground drive.
This teaches a horse to bend, balance and accept the bit in ways lunging never can. Lunging is just useless calories being burned, IMHO. I ground drive at walk, trot and canter.
Two years - birth through starting at 2 years old. Sorry to not clarify. Not everyone needs a "minimum requirement" of 2 years of groundwork. There is just a lot that an untouched horse needs to learn, and I think it is better to do it over the course of those 2 years rather than all in the last 30 days. What is starting a horse from nothing? - Ground control, bathing, trailering, farrier work, medicating/worming, sacking out, driving, exposing them either to shows/trails, desensitizing, tying. Regardless of the price of your horse or what you want to do with it, you still need all those basic things before you even get on.
Then there's the idea of fitness. No, I don't agree with senseless longing. My yearling longes, but that is just her final step. She is fitted by ground driving through the trails. Not only does it give her exposure, but also puts her through her cues. She is a sound and happy trail horse and loves it. She is also a show horse. Having control of your horse when you expose them to new things is important regardless of who or what you are. I just cannot imagine trying to cram all this information in 30 days, plus getting on them and riding them. Of course, a great trainer and a great horse can do anything! But a lot of trainers aren't great, and not all horses are either.
I also think a horse should be physically fit enough to carry themselves and a rider. Pull a horse out of the pasture - he's probably out of shape even to carry himself properly unless he's very well bred. It takes time to build fitness so a horse can carry a rider without the potential for injury, or bad habits such as inversion out of pain.
Any horse and rider combination can benefit from a relationship with a trainer. Not just a onesy-twosy relationship, but one where you actively communicate your goals and hopes. You don't have to be in training full time, but training doesn't end after 30 days no matter who you are, and it's always good to have someone on your side to take lessons with or to ask for help. I can't afford lessons or training, but I have many friends who I can go to when I need help.
And I treat all my horses like stars, I have both Minivans and Ferraris in my barn. That doesn't mean the Minivans don't get their oil changed regularly and are driven like crazy just because they are a cheap car. They get maintained like the Ferraris. Regardless of what your horse does or what your horse is, all horses benefit from good training. It adds value if you put it in. Selling a green broke horse is hard. Selling a pasture puff is even harder.
Sorry if I've come off as a snob.