Learn squid from YouTube and free course from udemy. not as easy as just load lol
1. way
you need a dedicated server with a fast line .
your need ip adresss that are clean.
your need squid loaded and understand the settings.
2. way
you can be affiliate proxies provider , you do ad5vertising sell the proxies get comission.
3. way
you can get a massive spool of proxies 10.000 usually around $200/m and you sell them to your own customers, but Thu there system.(( your in control price and amount they get, and auth with there ip to the proxies.))
all above are private proxies or ipv6 setup only.
resedentual are the most wanted and the best on the planet so far.
you can do the above as a afflicate and even setup your own but there very expensive ...
there are residential wholesale the startup around 10k .
good luck.
can cheek Google and do your own investigating.