I have around 100-120$ I can spend on a server, I'm only 13, but have a debit card so I can buy stuff online/ebay. Beginning to do tensorflow/machine learning/hosting some minecraft/csgo servers. I have a unused microATX case and a 500W 80+ white PSU (prob not the best for a server, but I have a limited budget)
My current rig is a i5-8400+16GB DDR4+RX 570, pretty decent hardware.
Want to have a server that I can leave on 24/7 for something. Want to get something like a dell r320 but those are a bit too expensive for me. Any reccomendation for other parts or places I can get parts for cheap/free?
thanks for your help, and please let me know if I messed anything as this is my first time posting
(I also have good experiance building PCs
For only 100-120? Eh...and you don't have an nVidia GPU (even a GTX750) lying around for CUDA tensorflow acceleration?
Alright, let's start with the small steps.
Buy an nVidia Jetson Nano (for 24/7 machine learning/tensorflow stuff - it has a CUDA friendly GPU), it's an ARM board, you can leave it on until the cows come home and it won't be obnoxiously loud or put a dent on the electric bill.
Get an Amazon EC2 account (you should qualify for free tier) and put your CSGo/Minecraft stuff there - your money should be enough for a year of a t1.small instance or 2. Virtualization is the way forward, and unless your dream job is to be a data center goon, not having to babysit hardware is often a very good thing. Actually, maybe your dad should sign up for EC2 and keep tabs on your spending. You don't want to accidentally spin up a t2.2xlarge instance that runs up the bill at 33 cents/minute/instance.
Hosting out of a university? In order to access your server remotely (ssh/RDP/VNC) you will need VPN connectivity (with an account there) to get past their firewall, and that requires you to be a student there. Hosting in your friend's house? You'll need your friend to give you remote access, and you will be subjected to his family's whims. If he gets in trouble for using too much power, everything is getting turned off, your machine included. Running tensorflow off your dad's work machine? Don't. Your dad might not be aware of the specifics of his workplace equipment acceptable use policies. You might end up doing something that can get him in trouble, especially if it throws a high CPU usage alert on someone's monitoring screen (I would certainly not be too happy if an employee from my workplace is using company property for doing something non-work related and draws my boss's unwanted attention. It's the same argument against running bitcoin miners at work - it's not your hardware to wear out, it's not your electricity to consume, and frankly, unless your job requires tensorflow, it'll be difficult to justify).
As for sources of free/cheap hardware? Dumpster dive, volunteer at your local non-profit with a computer literacy program, hang around community colleges/universities, and sign-up for internships (if such a thing is available to you). Some companies (like mine) have hardware that we want to get rid of - you just have to poke the right person and ask nicely. Just remember that shipping often exceeds the residual value of the hardware, so free is not really free.
Keep in mind that you are still at that age when people don't charge you for all the electricity you consume, or yell at you for all the server fan noise that your hardware makes. Once you are, you will be much less enthusiastic about running old server hardware in your home (I have no idea how your friend didn't catch hell from the parents for the power usage). I honestly don't encourage it, and unless your parents are okay with it, it's not a good idea (and even if it is, put it on a well ventilated shelf in the garage on a beefy circuit that is not connected to other stuff in the house) - run it by them first, give them an idea of how much it'll cost, and take this as constructive advice from a guy who used to do this in his youth living in a small NYC townhome, and doing it now as a married adult in a NYC apartment. Good habits should begin young, and part of that has to do with taking responsibility for things....things like accidentally tripping breakers in the house, generating high pitch howling from server exhaust fans, or running up hundreds of USD per month on utility bills for your tech toys. That has always been the dark side of running servers at home that people tend to gloss over, but it's real, and the earlier you are aware of it, the better it is for you.
Now if your dad comes in here asking for advice on what to buy his boy who is taking up an interest in running servers 24/7, I'll probably tell him to get a used Xeon-D 1541 box from Supermicro (quiet, performant, compact and easy on the wallet/circuit breakers), and install a mid-level nVidia GPU for tensorflow - barring that, maybe a Gigabyte Gamer Brix Super-NUC OR an HP EliteDesk 605G4 (with the MXM slot) populated with an nVidia GPUs onboard. The whole thing will be around 500 and good for the next few years.