[RC] horse purchase

[T.B.Pots]

Could anyone please tell me what the customary way is to try out a horse?   This is where I'm at:  I found a horse who seems to fit the bill for what I'm looking for.  The horse is located 4 hours away so I'd like to bring him back to the stable I plan to board at for a trial period.  I also plan to have him vetted out during this period.  So should I give the owner the payment in full even though the horse has yet to be vetted out or do I post date the check?  Or should I just put down a deposit?  If that's the case then what is an acceptable amount?  And , since I'm asking all these questions how long do you think is a reasonable time period to try out a horse?   Thanks ! Tracy