to the OP: welding grade is fine for torching and hopefully costs less than medical grade. As you most likely will be renting the tank, try starting out with a smaller tank (easier to handle) and get a feel for your usage rate. You can always rent a larger tank next time if you feel you need it.
Please make sure you handle the tank safely. The hand carts with a chain across are a good way to move them around. Always have the valve cap on during transport. Chain the tank to a solid surface (wall) while in use to prevent accidental tipping over. Below is a cut & paste from OSHA, it's all pretty basic and easy to do. Stay safe and GO MELT SOME GLASS!
OSHA's construction standard for storing compressed gas cylinders (for welding) are addressed in §1926.350(a), which states in part:
§1926.350 Gas welding and cutting.
(a) Transporting, moving, and storing compressed gas cylinders.
(1) Valve protection caps shall be in place and secured.
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(6) Unless cylinders are firmly secured on a special carrier intended for this purpose, regulators shall be removed and valve protection caps put in place before cylinders are moved.
(7) A suitable cylinder truck, chain, or other steadying device shall be used to keep cylinders from being knocked over while in use.
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(9) Compressed gas cylinders shall be secured in an upright position at all times except, if necessary, for short periods of time while cylinders are actually being hoisted or carried.
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(11) Inside of buildings, cylinders shall be stored in a well-protected, well-ventilated, dry location, at least 20 feet (6.1 m) from highly combustible materials such as oil or excelsior. Cylinders should be stored in definitely assigned places away from elevators, stairs, or gangways. Assigned storage places shall be located where cylinders will not be knocked over or damaged by passing or falling objects, or subject to tampering by unauthorized persons. Cylinders shall not be kept in unventilated enclosures such as lockers and cupboards.
(12) The in-plant handling, storage, and utilization of all compressed gases in cylinders, portable tanks, rail tankcars, or motor vehicle cargo tanks shall be in accordance with Compressed Gas Association Pamphlet P-1-1965.