Leasing can be great depending on the situation. Like a lot of people, I started out riding lesson horses and moved on to leases. Why exactly are you looking to lease? Do you want more saddle time? Want to move up?
I started leasing when I wanted to continue to advance my riding skills. Some trainers have very nice, A show caliber lesson horses, but I think most trainers just have lesson horses for beginner/intermediate riders and expect some kind of leasing after a certain point. Depending on what you’re planning to do with the horse, what level of riding you’re at, and how many connections your trainer has, you may be able to find a relatively cheap lease on a nice horse.
Due to financial constrictions, I could never afford to pay a lease fee on top of board, shoes, vet, etc. That said, I free-leased some very nice horses. I started with my friend’s nutcase horse, then moved on to an in-barn half lease on a wonderful hunter/eq mare. After that, I leased an older WB gelding, (who did the Maclay and USET finals in his prime), and finally a nice hunter gelding. With each lease, my riding progressed and I learned a lot, which I feel made what I was paying worth it. I wouldn’t have been able to jump over 2’6 on lesson horses nor learn to do a lot of other things.
If you would be leasing the same horses you ride now for the same amount of riding time, figure out which option is cheaper and go with that. Most leases tack on new responsibilities such as routine vet care, shoes, board, etc. so make sure you factor those in too.
ETA: As far as lease terms being followed, I made sure I had a written contract with the owner for each lease. All of my leases went smoothly, but I did make sure to communicate often and very clearly with the owner about what was going on with the horse. My only surprise charges were when my last lease horse went mysteriously lame and we had to go on an expensive fishing expedition to find out what was wrong, (he’s now sound as a low level dressage). If you have a clear, well thought out contract, I can’t see why you’d have any surprise charges only than for vet, and maybe not even that if you have insurance.