I don’t know how serious your pain is. If they’re minor you might try some self-care. If they’re really serious you’ll have to bite the bullet and talk to a podiatrist. Try to find a good one, they’re not all equal.
And I totally understand, medical costs can be ruinous in the US. It gets up to a few thousand dollars so quickly.
If the corns are the primary problem, you could start by trying to self treat those. You can just search for information online but basically you soak your feet to soften them up and then use a pumice stone to knock down the corns. I had some minor corns in and I was able to get rid of them by using a cheap pumice-like nail file.
I had metatarsalgia (inflammation of the ball of the foot) and my podiatrist suggested I try these:
You put the metatarsal pads behind the ball of the foot instead of directly underneath. What they do is lift the ball slightly so it doesn’t impact the ground as much. There’s probably YouTube videos. You can put them on the bottom of the removable insoles instead of directly on your foot. Obviously a podiatrist could potentially position or shape them better.
You can also buy over-the-counter orthotics aimed at ball of foot pain:
PowerStep® offers a range of orthotic insoles designed to help alleviate ball of foot pain so you can get back to doing what you enjoy most. PowerStep insoles are podiatrist-designed for ball of foot pain relief and prevention of Metatarsalgia and Mortons Neuroma.
powerstep.com
You can double up by putting the metatarsal pads underneath the orthotics.
The metatarsal pads and the orthotics did make my feet more comfortable, although I don't think they helped alleviate the problem.
And I would say that the orthotics help more than the metatarsal pads. I did use over-the-counter orthotics, but I also had custom ones.
I have a lot of foot problems, and ensuring the comfort of your feet is possibly the most important thing for a successful Camino.