Honestly… it’s a lot more than paying twice board and having a spare horse to ride.
Expect to spend WAY more time at the barn. Every bill will double, and somehow new ones will appear. If your current horse is easy, it’s almost a guarantee that the second one will bring more issues.
If you are in a new job that pays more, I’d assume you may need to be working more or will be more tired? At least that is my experience. I had one quirky horse and when he retired I replaced him with 2 relatively easy horses… I thought I could handle it after him, and I did, but I did not like it. Ended up going back to one. Maybe if both horses are pretty well educated and you have a flexible schedule… It’s just a lot of work.
That said, I actually own 4 horses… one out on lease, mare and foal with my parents, and I have a young gelding I am about to start. But only one that I am/will be completely paying for and riding full time. So take my answer as you will, as I’ve got backup horses to spare :lol:.
Edited to add:
I just saw that you are planning to 1/2 lease the mare. That will definitely help. As long as you are confident in her ability to get a continue to get leases. My horse on lease is pretty much a saint, and willingly will do a variety of jobs. I’m confident in his ability to continue to be leased.
Either way, good luck and let us know how it goes!