How can I get rich quick?
There are 2 "fast" ways:
Steal the stuff you want: You get it for free, BUT the shopkeeper will kill Link for stealing from him. In addition, every character in the game will refer to Link as 'THIEF' from that point on, effectively replacing his name in in-game text
Farm at the crane-game: This is IMHO the fastest way to get rupees but still takes some time and doesn't have any down sides.
Hold B to move the crane over to the exact center of the left conveyor belt. Now wait until the rupee's top is about to hit the end of the right conveyor belt, then quickly press A and let go immediately. Works every time.
Once you understand the timing of the crane game, it's easy to win consistently. But if you know where to look, there's plenty of treasure lying around Koholint. Most dungeons have one or two hundred rupees lying around as well.
There are a few ways to score some rupees, but if you rule out the Trendy Game, I'd suggest explorin' the map for some treasure chests. Here's a map with some locations for ya. Note that on about half of the screens, the chest is in a cave/dungeon.
The screens with color are places with chests. Squares that are split in halves/quarters/fifths have multiple chests on them. The colors code for the amount:
- Red: 20 Rupees
- Purple: 50 Rupees
- Green: 100 Rupees
- Orange: 200 Rupees
Note that a lot of the screens with multiple chests are in dungeons. Of note are two in particular with a whopping 200 rupees: one in L:3 (Key Cavern, in Ukuku Prairie near Mabe Village) and one in L:5 (Catfish's Maw, in Martha's Bay near Animal Village). If you found the Map and Compass in those levels, it shouldn't be hard tracking down remaining chests. L:5 in particular has a pile of wealth waiting for you to claim it.
Others to note are 100 in the Dream Shrine in Mabe, a couple of 50s in caves near Mabe, and a few up in the Tal Tal Heights/Mountain Range regions. If you just got the Hookshot, there's a chest that wasn't obtainable on your first time passing by in plain sight up in the mountains. There's also a cave in the Mysterious Woods that requires the hookshot to get with 50 -- it has stones surrounding the entrance and is a screen right of where you got the key for L:1.
There's also a screen in the Tal Tal Mountain Range with 5 chests in it. To find it, go a screen right from where you jump down to get to L:4 - Angler's Tunnel. In a cave there, you'll see a patch of sand surrounded by water. Bomb the wall there and proceed through the cave you reveal. When you first get to the screen with 5 chests, ignore them all -- don't open a single one. Just push aside the blocks and try to go out the southern exit. Go outside and then back inside to reset the blocks. Now you should be able to get all five for a total of 100 rupees. If you tried openin' them on your way down, you'd find yourself one chest short (only 80 rupees).
Also, just so you know, if the miniboss in question is the Armos Knight in the Southern Shrine, you can actually damage it with charged sword attacks. It might take a few hits, but it's totally possible to do without the bow. The bow's actually pretty much optional -- if memory serves, it's only 100% needed for a Heart Piece in Animal Village, a key in L:8 (which has a bevvy of keys), and a quicker way to navigate L:8. Every boss that seems to need the bow to kill actually has another method to kill it. The bow does make those encounters easier, though! :)