Hi @Brian_Luu, here’s some arguments to throw your father’s way.
#1 - 3D Printing is a massive learning experience and the technology is becoming more and more common in all sorts of businesses; learning now could give you a substantial step up for later education (a lot of students use 3DHubs to produce visualisations/prototypes) or work.
#2 - The printer could pay for itself quite quickly if you produce high quality prints. OK, it’s not going to be overnight, but I recovered the cost of my first printer, and all the filament I bought within 5 months, so if cost is an issue, that’s a good argument.
#3 - 3D Printing allows you to expand your other hobbies and interests. I got into 3D printing because I was building electronic devices and needed a quick, cheap way to produce prototype cases and accessories. Without the printer I couldn’t have realised my other projects, so it was a tool just like any other. As it happened, I became more interested in printing (and it paid better) than the electronics themselves…
#4 - Becoming a good 3D printer means knowing more than 3D printing. In my opinion, the best printers (humans) are those that understand their customers and what they need. It’s one thing to take a file, load it into some software and press the go button, it’s another to actually engage with the client and help them achieve their goals, possibly, sometimes, by telling them that 3D printing isn’t the best option (or more often, that their model won’t work). Gaining confidence in dealing with clients will help you in anything you do as you get older and what you learn from working with those clients can help as well.
#5 - ANY new learning is worthwhile. Even if the lesson learned is that 3D printing isn’t for you, it’s still valuable learning. I don’t regret any of my (very many) failed enterprises (I’m very old), because each taught me something, even if those lessons were painful and/or expensive.
OK, that’s all the good stuff, now I have to add some caution…
It’s all going to take time and there are going to be a lot of failures and problems. You’ll need patience and commitment to achieve long term results. It’s very exciting (to some people like us!) but you have to control that excitement and set a steady pace. If you’re thinking you’ll be posting award winning models to Thingiverse this time next month, think again. I have some of my earliest prints lying around my office and I look at some of them with horror; how did I ever think that was a good print?
It’s messy. FDM printers are probably the least messy of the technologies, but you’ll still end up with bits of filament all over the place. In your clothes, your hair, the carpet, your food… 
It’s smelly. Some filaments are worse than others, but even the best leave a fairly unpleasant smell in any room they’re used in. It’s noxious. Fumes from printing can be harmful, so ideally you need good ventilation while, ironically, a lot of printing requires a draught free environment. It takes up more room than you think. Don’t look at the printer and think “Hey, that’ll fit nicely on that table.”. You need space to clean prints, store tools, store filament (and store it so it can be kept dry) and you’d be surprised how much filament rolls start to eat up. At the start you’ll need lots of little bits and pieces; tools, chemicals, tape, glue, spare print bed sheets (if applicable). It can be noisy. Some printers are reasonably quiet but most make enough noise to be disturbing in a quiet environment and the vibration can find its way a surprising distance across a quiet house.
Anyway, that’s enough to chew on, I wish you luck. Let us know how you get on.
