Hey! Hi there, we and our proxy farmers have tons of experience in this field
I’ll focus on
mobile proxies specifically. They’re in high demand because only mobile proxies truly avoid bans on social networks and other picky resources.
For an individual proxy farmer, mobile proxies are the easiest option, since
you alone definitely can’t legally farm residential IPs. And
datacenter IPs get banned so fast, they’re hardly worth it.
About your questions in mobile proxy case:

You can set them up on mobile
phones or
USB modems -- basically any device that can use a SIM card (real or eSIM). We went with
phones because they’re easy to start with (everyone has some old Androids lying around) and simple to scale. Plus, supporting 5G is often a must for clients.

You can either
build your own solution (using open-source tools like 3proxy) or pay for a
subscription to a ready-made service. DIY can be cheaper if you know network tech and coding, while the subscription route is hassle-free and lets you start right away.

The mobile IPs come from the
SIM card itself. A single SIM can give you access to a huge pool of different mobile IPs! Every time you reconnect to the cell tower (reboot your phone or toggle airplane mode), you get a new IP, so your proxy’s IP also changes.
(!) Some mobile operators do NOT rotate IPs when reconnecting, so you have to test.
I’d be happy to keep this conversation going -- it’s a massive topic with lots of nuances.
It’s also a great business -- our proxy farmers are growing fast and the market is taking off!