Team Aqua Hideout increases the Retreat Cost for certain types of Pokémon - how does this affect a Pokémon that has a Poké-BODY that reduces the cost to zero, or a Pokémon that doesn't have a cost to retreat?
If a Pokémon doesn't have a Retreat Cost, it now has a cost of one. If a Poké-BODY reduces the cost to zero, the cost remains zero.
Source: Team Magma vs Team Aqua FAQ (2004-03-04)