I wouldn't go into collecting if you're looking to make cash. MtG is probably better for that with their outrageous card prices. The problem with pokémon as a cash-card enterprise is that the game is in flux much more often than the other games out there as different strategies rise and fall in power, popularity, and rarity, and older cards get cycled out. As an example, the mainstay for most decks, Uxie from Legends Awakened was better than 10 dollars for a long time because of how useful it was, but then it got released as a POP league promo, which dropped the rarity of the card significantly, and now it's been completely rotated out, making it all but worthless to anyone playing current format except as a collector's item, and then you're banking on somebody putting sentimental value in a card that's no longer playable which is anything but reliable for pricing.

TL;DR- if you're gonna get back in, get in for the fun of it, and to play for yourself. It's really pretty fun if you've got a group to play and practice against.

This isn't quite so related, but with the beta launch of TGC Online and that upcoming pack in Japan with a DS "tutorial" for the game, it looks like we may at last be getting a TCG game on consoles/handhelds in the near future, so there's also that.