I have bought several used Canons off craigslist for under $50 that I use for time-lapse photography.
That would be a cheap way to start and later you could get a more expensive camera if you wanted, but CHDK gives the lower-end Canons most of the features of a high-end camera.
A lot of mid range DSLRs have these features. You can get better lenses and other stuff as well for a camera vs video camera.
Also remember, no matter if the camera is undercranked or overcranked, you can always fool around with it in editing to manipulate what you’ve got.
http://chdk.wikia.com/wiki/CHDK
You can get cheap but quite adequate remotes with intervalometers for many dslrs for $30 to $50 dollars from places like B&H or Adorama or Amazon.
For high speed slo-mo, something like the Casio EX-FH100 or EX-ZR100 may do the trick, although at the expense of resolution, 1000fps all but unusable, 224 x 160 at 420 fps not bad, as good as you got with analog tape, looks like 4x3 aspect ratio. Check out the reviews & samples on youtube.