A common question that beginners have, is the hardware they need to getting started. You can start self-hosting with any hardware you have lying around, that could be a Raspberry Pi, Laptop or and old Desktop. Just watch out for high electric costs if you're running old inefficient hardware.
I would say that a Raspberry Pi 4 is a great way to get started, it has a quad-core processor, Gigabit Ethernet and the option to use an SSD instead of an SD card for faster Read/Write speed. As the Raspberry Pi uses an ARM CPU you may run into issues running some applications. This is becoming less of an issue as the list of ARM-compatible applications is growing by the day. The Pi 4 has a low power draw which is something to consider if you plan to have it powered on 24/7.
If you don’t like the sound of using your hardware or you have poor upload speed. The Cloud could be a better option, you can rent a basic Virtual Private Server (VPS) for less than £5 per month.
This is where a Cloud provider will own a physical Server and then run visualization software on top deviding it up into multiple Virtual Machines (VM's) this gives you all the benefits of the cloud without the price tag.
The cloud can provide high availability and a speedy internet connection. You will need to have trust in the Cloud provider as they own the hardware and the internet connection. Some may argue that if you’re using a VPS then you aren’t self-hosting, which is technically true.