You may have come across in your research that it takes approximately two years to train a horse on barrels so they are "finished". Do you have that figured into your plan?
At what level do you want to be competitive? I know you said local gymkhanas and barrel races, but (1) do you want to go for fun [and donate your entry fee] or (2) do you want to WIN?
You didn't mention those goals. That will influence how expensive said horse is that you plan on buying. Sure, any horse is capable of barrel racing, but a prospect that is bred for barrels will be more expensive than one that just has "general" breeding.
If you plan on buying a horse that is already started on barrels, it depends on your area, but you are probably looking around $5,000 and up for a started barrel prospect. It will usually be around $10,000 for one already running and placing in the low end (3D and 4D) and the price continues to go up from there. It also depends on what AGE of horse you have in mind.
∞•*˚ Βгįťţαňγ ˚*•∞
It is not enough to know how to ride; one must know how to fall.