Learning "impractical" Instruments Options

[river]

okay, so the other thread on buying a piano made me curious...

say i wanted to learn the piano, or perhaps the organ, or some other instrument that's large and expensive even at the low end. i can't just go out and spend £5,000 (or whatever a usable piano costs) just to see if i want to actually play it, and i assume even serious organists don't have a pipe organ in their house.

so, what would i do? just play in lessons and not practice to start with? find time on someone else's instrument? rent one? use a digital piano or keyboard? i assume the latter isn't an option for the organ--or do digital organs exist? can you learn basic manual skills on a keyboard or piano?

okay, that's enough questions for now.

(to be clear, i'm not planning to play the piano, just curious.)