You can wake board behind anything. A normal runnabout wont have the shaped wake of a dedicated wakeboard boat, but depending on your skill level, its more than enough to get you up and having fun. You can get a universal tower from anywhere between $1000 to $3000 plus accessories. If you want a bigger wake down the line and your motor can handle it think about adding a fat sack ballast.
Check out http://diywake.com theyre a good place to start for what you need. I added a tower to my monterey recently. I went local for the tower but I got the racks and a mirror from here. And a friend of mine bought 4 of the tower speakers. Everything is extremely nice and high quality.