I share the same fears as you.
Although I've been pretty much lurking on forums like this for years now out of nostalgia, I only recently took the plunge and purchased some hardware.
I called out to all my old Amiga buddies looking for hardware stuffed in their basement and also kept my eyes opened on eBay and Craigslist. I got fantastic deals on a near mint 4000T, a neglected 3000, and a busted 3000T.
My thoughts going into this were to be patient and not over pay for anything. Time aside, I know I could always resell anything I have and get my money back plus more. As for the time I've put into it, it's been frustrating at times but fun always - so I don't regret it a bit.
I've finished off (I hope) my 4000T and 3000, and trying to finalize my 3000T at the moment. I haven't actually played a single game yet, but the true fun for me has always been the tinkering.
I love WinUAE and might get a FPGAArcade, but it's not the same as real hardware (both good and bad aspects).
As for getting bored and selling the systems, I hope I'll never need to sell for cash and space for me is not an issue, so I'd like to think I'd keep them indefinitely. Like collecting antique cars I think uncommon systems will only increase in value as machines break and they get more and more rare. I hope to keep mine in good condition.
My advice to you would be the same - use emulation, take your time, and don't overpay. There are deals to be had out there if you're patient.
Good luck!