Depends on where you live and what type of barn you are looking to go to.
Cost
Lease = Free up to and more of 85,000 year
Buy = Free up to and more 300,000
You can get a free lease for an old school master type horse but if you are doing the A circuit I have heard of yearly leases from 45,000 to 85,000 a year. I am assuming your are not looking for this
Boarding vs. Keeping your horse at home
Boarding - from 350.00 a month for stall, feed, and cleaning up to 700.00
If you are in a full training program - add 500.00 to 1,500.00 for grooms and lessons per month.
Horses at home - depending on your location would cost 125.00 for 5 bails of grass/alfalfa hay. Bedding shavings at 8.00 a bag around 160.00 a month
Additional if you pay someone to feed and clean for you around 250.00 a month.
Showing
Depending on where you show
1 day Schooling shows
20.00 a class
trainer fees if you have a trainer 50.00
trailer fees - 200.00 - 500.00
A rated week show
3,000.00 a week
Trailering, braiding, grooms, trainer, feed, stall, classes.
Supplies/Care
Hmm - depending on what you have already it is a pretty big list.
Bridle, saddle, blankets, pads, splint boots, polo wraps, riding boots, helmet, gloves, breeches, hunt coat, ratcatcher, brushes, fly spray, shampoo…etc etc
Additionally -
Vet - you just never know and must be prepared. (insurance can help)
Farrier - 150.00 every six weeks. or more depending on your horses needs
OPINIONS:
Find a good local trainer you like and work with them.