Welcome to the boards & hobby!
I'm 14 and I'll tell you it's not the cheapest hobby. The Porcupine puffer is an awesome fish but will get huge. As juviniles they will need at least a 125gal and will eventually need a bigger tank. The bigger the tank the easier it is. The bigger the tank the less the problems spread, the smaller the tank the quicker. With big tanks you don't need to do waterchanges as much as you would with a small tank where you would be doing small weakly changes. There are 3 main types of tanks:
Reef Tanks-have corals & anemones but require special lighting, a lot of water movement, and certain fish such as triggers, puffers,buttefly fish, most angels, and lions will eat the coral.
FOWLR ( Fish Only With Live Rock)-This tank needs less filtration and consists of peaceful community fish
Aggresive/Predator Tank- In these there are puffers, lion fish,eels,triggers, and many aggresive fish. They will eat shrimp and all other small fish
Many companies sell setups which are called nano cubes (check out the nanocube forum) and they have everything you need except a heater (runs for like 20$) the sand, live rock and your fish. A 24gallon tank would be the size I would look at if you have room and it's nice and small. It will cost like 250$ and will come to be about 350$-400$ after you put in rock and water. For that sized tank I would do weekly waterchanges of 5gallons and more when you test the water and it's dirty. Total it will be 1-2hrs a week depending on your fish and special needs. Many of these fish vary in how long they live. Fish which are breed in tanks are hardier and live longer, fish from the ocean get a bit more stressed because they need to get used to captivity. Fish can sometimes live 10years. In a 24gallon tank I would get Live Sand, 20-30lbs of LR "Live Rock". You could have a few small fish and a cleaner shrimp. You could go with 2 clown fish, a purple psuedochromis and a cleaner shrimp. You could also get a buch of corals in there to. Welcome to the hobby & feel free to ask more questions.
Yimmy