You can do tintypes in a Kodak Brownie box camera with surprisingly good results. Maybe $5-$10 at a thrift shop. I'd go that route with a Bostick & Sullivan kit to see if you really like wetplate. That's probably the least expensive entry.

I know people who use Holgas, Hasselblads, Brownies and other cameras for wetplate. And of course, if you have a large format camera that opens up lots of possibilities with modifying film holders to wetplate, adapting dedicated wetplate backs, using wetplate era lenses and so on. But, to get started you just need the basic chemistry, some trays, a darkroom, and a cheapo camera that you don't mind getting some silver nitrate stains on.

One of the most popular cameras at the workshops I've held has been a Brownie 3B that I removed the aperture baffle from. Using the meniscus lens wide open produces soft, dreamy, diffused images. Stopping down to f/16 or so give very sharp results. Think of all those snapshots from the early 1900s for an idea of how good the image quality can be.

You can make a pretty cheap darkbox out of a large shipping box and old changing bag. An led flashlight (torch for those across the pond) is all you need for a safelight or a piece of red acrylic sheet or stained glass can be taped to a hole in the box.

Be sure to read through my online article (listed in my signature below) as an introduction. Nothing beats a workshop but if you really can't make one, get John Coffer's manual and DVD set. That'll tell you everything you need to know.

I'd avoid the Rockland dry tintype kit. Google it to see many discussions of problems with it.)