If it was me, I would start by learning how to fix easy stuff like replacing HDMI/SD Card/USB ports on Xbox/PS5/Switch/Steam deck and other expensive smallish electronics.
Customers can drop off their broken device at your place and pick it up the next day, some people might mail it in, maybe you go the extra mile and do pickup and delivery.
You need steady hands and good eyes, total equipment cost is under $500, there are alot of youtube videos you can learn from.
You can later expand to more complex fixes, replacing batteries, and data recovery. You can also purchase cheap broken devices and fix them for resale.
Over the long term I think the fixing industry will grow; most devices these days are powerful enough to last several years, devices are getting more expensive, there is a huge positive environmental impact that I think eventually will be recognized by the government and grants/tax credits will follow.
You make money, the customer saves money, the environment wins, the only losers are Apple/Google/Samsung/Sony etc...
One of my ideas is to buy van, drive to the customer's place, pick up the broken device, park nearby, do the repair and give it back to the customer.