Buyer's guide

The short version of what we'd tell you on the phone.

Containers

Size: 20 ft fits most homes and job sites; 40 ft is the best price per square foot. High cubes add a foot of height for shelving, offices and equipment.
Grade: One-trip (near-new) for anything people will see or work in. Cargo-worthy for heavy use and export. Wind and watertight (WWT) for budget storage.
Delivery: Tilt-bed drop needs about 75 ft of straight run for a 20 ft and 110 ft for a 40 ft, plus 14 ft overhead. Level the ground with blocks or gravel pads under the corners.

Bumper pull or gooseneck: Bumper pulls use a standard receiver and suit 2-horse loads and smaller trucks. Goosenecks need a bed hitch but tow more weight more steadily.
Load type: Slant loads fit more horses in a shorter trailer; straight loads give each horse more room and an easier unload.
Construction: All-aluminum trailers are lighter and don't rust; steel is stronger for the money but needs more upkeep.
Weight: Check the trailer's GVWR against your truck's towing capacity with horses, tack, water and hay aboard.

ASME vs DOT: DOT cylinders (up to 420 lb) can be transported and refilled at a station. ASME tanks stay put and are filled on site.
Usable capacity: Tanks are filled to about 80%, so a 500 gallon tank holds roughly 400 gallons of propane.
Above or underground: Underground tanks keep the yard clear and cost more to install; above-ground tanks are simpler and easier to inspect.
Installation: A licensed propane provider must set, connect and fill the tank. Local code controls clearances from buildings and property lines.