There is nothing morally or ethically wrong with humanely euthanizing two older, unrideable horses that you can no longer afford to care for at the level which they require and have become accustomed. In fact, it’s one of the kindest and most responsible things you can do as a horse owner.
It’s also one of the hardest.
I will not tell you what to choose, as that must be your own choice for your own reasons. But can you bear the idea of these horses going to homes where their needs may not be met? Where people may not care for them as much as you do? Because the fact of the matter is that unless you retain ownership of them both, you cannot control what ultimately happens to them. The ONLY way you can do this is to lay them to rest.
Now. If neither of these options sits well with you, I’d suggest coming up with some ways that you can keep them and afford them. You say you’re being forced into retirement. Does this mean you are unable to be employed in any capacity? Are there any possibilities for you to work or earn money in retirement that can be used to pay for the horses’ retirements? Are there any boarding possibilities with self-care, or maybe even helping out with feeding, etc. to off-set the cost of board for your guys? Any hobbies or interests that could lead to an income stream? Any part-time employment that could supplement your retirement with all or part of that $18k/year?
One of the reasons I won’t be able to retire when I’m eligible for full retirement (7 years from now) myself is the horse expenses. If I didn’t have my gelding, I could swing it, but he’ll be 24 and I will continue to pay for him to live out his life at the self-care barn. I’ve luckily been able to make a little extra cash out there taking care of other people’s horses, and honestly, if I could increase that hustle (which I could, the guy doing most of it is in his late 70s), I could probably retire on time. I can also substitute teach (full-time teacher here), or work at the vet’s office or whatever. I won’t stop working when I retire from my career, especially if I still have a horse.
All of this to say, if you are unable to supplement your income or find a situation that allows you to afford the horses, then euthanizing one or both of them is absolutely a legit option. I would respect that decision much more than passing them on to an uncertain future.
I do not envy you this decision and wish I could give you a big hug. Out of the many blessings my late heart-horse gifted me with, he took this heartbreaking decision away from me the day he broke his leg in a freak pasture accident. He was 22, his older pasture mate had preceded him in death two years prior, and I still have his younger pasture mate. His accident prompted a turning point in my life that led to me selling the farm I’d had for 20 years, moving to a small house in town, and boarding my remaining horse. I also got a new (better) job just down the road from where I live and where the horse lives. It worked out so perfectly. The WORST thing I could have imagined (finding my beloved gelding with his leg horribly broken) paved the way for more blessings than I could have imagined. I will never be convinced that it was all coincidence. That horse is still blessing me every day, 6 years after his passing.
Whatever you choose, it will be the right choice. Trust in that. And know that your horses are fine with whatever you choose because they have no concept of the future.
Hugs to you.