Warhammer and 40k are fun if you've got the money to invest in gathering an army (which can be partially alleviated by buying used), if you've got the time to invest in assembling and painting said army (which can be partially alleviated by buying used or, if you've got the budget, paying someone else), if you've got the capacity to keep up with the rulebooks in order to stay with the SotA curve (which can be partially alleviated by having a good gaming group), and if you've got regular opponents who will (a) be able to play often enough to let you have fun with it, and (b) not be douchebags with the rules, wreck your fun, be hypercompetitive, etc, etc.
It's like most wargames in all those ways, basically, with the caveat that you'll tend towards needing a larger army, but will tend towards a larger used market (to somewhat make up for it) when compared to the likes of Warmachine or Hordes.