You can run one, something like ByteLixir, Traffmonetizer, Honeygain, Pawns, there are lots more, just google "share my internet for money"
What will you be proxying? Nobody knows! I haven't had the police at my house yet.
Seems a great way to say "fuck you" to companies that block IP addresses.
You may see a few more CAPTCHAs. If you have a dynamic IP address, not many.
How much can you make if you run all of them at the same time?
Doesn't the ISP detect them?