* A work of art that's appraised at $10,000, for example, but that's priced for sale at $5000, is not necessarily a bargain. As stated above, a retail or insurance appraisal can be many times the fair market value of a work of art. Always determine fair market value first, no matter how big a bargain the seller makes you think you're getting.
In general the aircraft must be at least 500 feet away from any person, vessel, vehicle, or structure. In congested areas the aircraft must stay 1000 feet above the highest obstacle within a 2000 foot radius of the aircraft. There are special rules for helicopters that allow them to fly closer than these general limits.
Most general aviation planes use propellers and must cruise at lower altitudes. For example, a Cessna Skyhawk has a maximum operating altitude of 13,500 feet. Planes that fly at higher altitudes must have pressurized cabins to keep the pilots and passengers safe and comfortable.