Yes, you can use a saw to cut metal pipes. The best saw to use is a reciprocating saw, but even a fine-tooth hacksaw can get the job done. No matter which saw you use to cut metal pipes, wear protective gear, like work gloves, safety goggles, and ear plugs. Apply a firm, steady pressure to the tool, and always ensure the pipes are secured so they don't move while you make the cuts.

Cutting rectangular ductwork requires careful measurements and the right technique. Use a measuring tape and pencil to mark the cutting lines accurately. Tin snips are excellent for straight cuts on smaller ducts. For more extensive or thicker rectangular ducts, a reciprocating saw with a metal-cutting blade is effective. 

Ensure the duct is well-supported and secure while cutting to prevent wobbling and maintain precision. After cutting, use a metal file to smooth any sharp edges, ensuring safety during installation. 

Costs depend on unit complexity, labor, wall mounting needs, and additional accessories like floating shelves.

Your typical household tools will not cut a metal pipe. To cut a metal pipe, you’d need more specialized tools like a pipe cutter or circular saw. Do not attempt to use these tools without taking proper safety precautions and wearing safety gear. It’s usually safer to let a pro cut a metal pipe, especially if you’re not confident in your skills with a heavy-duty saw.