If you're mechanically minded and enjoy fixing things, there can be no more rewarding experience than providing a patient with useful medical equipment. Depending on the patient's medical insurance and coverage guidelines, they may not be eligible for a replacement piece of equipment, so offering this service can really make a difference for a patient's ADLs (activities of daily living).
Become familiar with all types of durable medical equipment. There are many modalities of equipment: respiratory, orthopedic, enteral, neonatal, renal, radiologic, etc. Some of these treatments will be home-based while others are available in a clinical or hospital setting. Decide if you want to provide your services on-site or in your home in a workshop setting. For example, repairing an x-ray machine will require you to be on-site, whereas diagnosing and repairing an oxygen concentrator that's out of warranty can be done at home.
Volunteer at a hospital or out-patient facility to get an idea of the patients' use of the equipment and how it works. Hospitals generally have a "consignment closet" that dispenses medical supplies for patients to take home, so these facilities are often the primary providers of such items as crutches, walkers and commode chairs. Long-term care facilities have equipment that needs to be serviced. Offer your services to inspect and fix any items in your realm of knowledge.
Take some training courses if they are offered in your area or are available online. It is suggested that you have some familiarity with the medical field in which you'd like to specialize. If you want to focus on respiratory equipment, take classes in pulmonology, sleep apnea or lung function. If you enjoy working with children, familiarize yourself with asthma so that you can work with nebulizers and aerosolized medical devices.
Apply for a job with a durable medical equipment company. They will train you on the job as a technician. You will be working with a wide range of patients, in both acute settings (coming home from the hospital) or chronic settings (delivering oxygen tanks or enteral supplies). Some repairs are done back at the warehouse, but generally the items are covered under warranty or are sent back to the manufacturer for repairs. This type of job will give you invaluable experience when it comes to quick fixes, though, as sometimes a technician will be sent out without loaner equipment and will have to perform repairs on the fly.
Contact manufacturers of specific devices you'd like to work with and see if they have a training program available in your local area. Working with a manufacturer will shield you from any liability issues with regard to repair work. Oxygen device manufacturers are always looking for sales representatives; so if you don't mind mixing sales with repairs, this could be an ideal fit.
If you will be going into business as a sole proprietor, contact an attorney who specializes in small businesses. You will need a release of liability document drafted that the patient must sign before repair work is done. Ask the attorney if you need to incorporate as an LLC (Limited Liability Corporation) to avoid potentially onerous financial expenses.