for slow motion, you need sharp image, means lot of light, closed lens (f11 and more) , high speed shutter (100 and over) , progressive picture.
Aslo depends the lenght of final sequence, knowing that 5 sec is already pretty long, if you slow it down by 10, a shot of half sec. is enough.
Some digital picture cameras are able to shoot 120 fps or even 300 fps at decent resolution (640x480), but it is still low comparing t full HD.
I think at 120fps you should get already pretty nice slow motion if you boost it to 240fps with twixtor.
if you want full hd at 120fps or over, be ready to spend +$10.000.
if you want to stay cheap, the Casio Exilim is probably the best you can find.
The best guess is to shoot 1080i60, then split fields as pictures, so you get 1920x540 at 120fps. for cheap it is the best you can do and loosing vertical resolution should not be a big deal.