Take your time searching carefully through candidates, and enlist the help of a qualified friend or professional who is familiar with the breed. Friesians are an expensive breed of horse, and low prices may be hiding lamenesses or behavioral problems.
Be willing to travel to find an affordable Friesian. Although they are popular, they are still fairly rare when compared to other horse breeds. Your local selection may be limited.
Consider a foal or young horse that has not yet been started under saddle, but only if you have the skills to start it yourself. Paying a trainer to start it can be at least as expensive in the long term as buying a started horse.
Always pay for a pre-purchase exam to make sure the horse is healthy and sound. Most horses have some issues, but they should not be serious enough to prevent you from using the horse as intended.
Learn about the Friesian registry, and consider a horse from B-Book II lines. Although these horses have not been registered since the end of 1994, some unregistered horses may be available and should be less expensive. However, these horses are not suitable for breeding. Friesian crosses are also generally less expensive than purebred Friesians, but they may still have the desired look.