There are some ‘legit’ apps that do this, for the purpose of targeting you with ads. Hard to believe, but some people want to be specifically catered to with ads. There are also a lot of poor people who sign up to these things to make a few extra dollars and get free samples from review sites, which is kind of in the same category of website/app. For example I knew someone who got paid to review Chromebooks or Netbooks or something from a Chinese manufacturer. There are survey sites and apps too, and other data collection apps which pay users small amounts of money for small amounts of data.
However what your cousin was doing sounds even more sketchy than that. It sounds like the sort of thing that will somehow turn out to be crime.
I’ve learned that it all starts with the phone, and the internet router. The phone is essentially a little computer that people use as a wallet. Phone number is connected to almost everything people do. If someone has a smartphone they should update it every 5-8 years, even if they don’t use online banking.
Personally, if I didn’t want to buy a smartphone I’d just get a fliphone. Those are like $15, $20. You can afford to buy one of those every 8 years. Tracfone sim cards are essentially disposable so it’s possible to use a phone number to create an account and then discard it if needed, or keep it active indefinitely. When I used Tracfone, I’d pay by the minute or by the text, and the time would last until used. I’d pay $20 once and get say 60 minutes of talk and however many texts. At the time I communicated mostly on messaging apps so I’d use the phone number for things I’d need a phone number for, like the doctor. The smartphones are like $40-$100.
I wouldn’t use fake identities for e-commerce but rather I’d choose a trusted e-commerce platform, use a fake email and phone number because they now demand both but use your real name and address. I don’t know how you’re getting things on e-commerce using an alias, because they need to be able to send you the thing you bought. There’s a service called Hushed, requires a tablet or phone, which sells phone numbers in packs of 1-3. 3 pack of phone numbers is $15, so you could have a phone number for personal use, a phone number for work, a phone number for e-commerce. There’s also MySudo, which sells 9 pack of email/phone number aliases for $15. With Hushed it’s possible to login on other devices but MySudo is device encrypted and requires a QR code to sync a limted number of devices.
If you’re interested in investing, want to use a mobile device for some reason but don’t want a phone, you should get a fliphone and a tablet instead of using a smartphone. A lot of smartphone apps, including those for online banking or trading, are also on the tablet. Tablets are a lot more advanced today than 5 years ago, and they’re more like ‘lite’ computers, but they have the same smartphone apps a lot of the time. But, you’d have to feel comfortable spending $200-$800 every 8 years on a tablet instead of a phone.