Questions about horses?

Ok so my mom and dad finally agreed to let me get my own horse as long as I buy it with my own money and work for the food and care. Im planning to adopt a horse and have already picked out a few but I have a few questions first. How old of a horse should I get if I still want to be able to ride it? How much is it usually per month to feed a horse and what kind of hay and grain should I buy for the horse? I plan to feed it at least 3 times a day. And lastly how much is it in bills for Vet care, farriers, and dental care? Please answer my question and give as much detail as you can into anything important that I should know. And just so everyone is sure Im not an amateur horse owner I know how to ride properly and groom a horse properly.
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All of these questions depend on what horse you ultimately buy. Your best bet would be to ask your trainer to help you begin your search for a horse. Just knowing how to ride and groom properly doesn't make you ready to purchase a horse. :)
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