you can get one by beating all of the trick master's challenges. i think you can get it at the lillycove megamart sale thing too. . .
yes
Unfortunately there is no TV in Ruby/Sapphire/Emerald for a secret base. Many people worldwide will be upset. :(
u can buy it in slateport
for your secret base you can make one by getting the TM secret power you can buy it in slateport city outside market
fromthe pretty pettle flower shop near rustboro city
First up need to beat the game, then go to lily cove city and buy boards.
you just buy it from a person underground (\__/) this is bunny (='.'=) (")_(")
You have to buy stiff boards from the lily cove departments store sale. its shown on the TVs but it is rare. they will cover the holes and let you walk into those areas.
you cant you need to buy the TM or get it from the guy staring at the pine tree by the desert
no
To get an underground secret base, you have to go down there and buy it from a hiker who is selling Traps.He should have a Digger Drill for sale.Buy the Drill from him, then use in on any random underground wall, and... BING!Your secret base is born.
Even though I don't play Pokemon Diamond, I know you buy it on the fourth floor of Velistone Department. They will then transfer to your PC in your Secret Base.