I've done it, can't be hard. A good book is Bickford vol. I - that will get the basics of fingering, tremolo etc. down quickly, and if you can't read standard notation you'll learn it quickly as well. It's an old classical method, so it's much more universal than a bluegrass method would be. The only basic thing it doesn't cover (IIRC) are basic chord fingerings.
You don't need a $7000 F-style mandolin unless you want to play bluegrass and need to compete with loud banjo players.
Do you want to go electric? The Epi Mandobirds have a pretty good reputation among mandolinists, but I haven't really played mando in five years, so... With electrics, 4 or 5 strings is good - 8 is more difficult to get a good sound out of - and you can use any guitar amp.
With acoustic mandos, avoid old bowlbacks unless you really know what you're doing, as they were built for much lighter strings and most have been destroyed by heavier strings meant for Gibson-style mandos. There are plenty of basic Gibson A copies that are cheap and decent, though, and flat mandos are even cheaper. If you need to amplify an acoustic mando, any acoustic instruments amp will work, or you can plug straight into a PA. Any guitar or bass amp will also work, it'll just sound a bit less natural.
P.S. For no good reason, here's a mandobass:
And slightly smaller, the mandolone:
