The cheapest way to get into IR is to buy a manual film camera and load it with IR film. The camera will set you back maybe $80. I've shoot IR transparency and BW Negs all you need is an old Nikromat or the like and an IR filter over the lens
If you want digital then what they do is remove the filters that are in front of the sensor. The people who do this are "lifepixel.com" They can do the work for you are they have instructions and parts on how to modify your camera yourself. They will do it for about $350 or sell you the part for $180. Plus you'd have to supply a camera.
Like I said, film is way cheaper. (and it's "full frame")
While I absolutely agree with you in recommending film, over time the cost of film and development can start to build. Not to mention the cost to either print and scan or develop and scan (even if you buy your own scanner).
A used Canon XT is about $300 on eBay (or so it seems). Then you have the $325 or $180 fee from lifepixel, depending upon whether you want to do it yourself or have them do it. I'm going to attempt to do it myself but I'll have someone watching me who is way more qualified to hold a screwdriver than I am! You're up to $625 if you have someone do it. That is your final cost no?
Then there's the film way. You can find a film camera for say $80, then there's the filter (red #25 I think) then the film. For Kodak HIE I think you'll be hard pressed to find much of it. I think Kodak discontinued it some time ago. Ilford put out that nearly shameful but passable SFX or whatever and I think that's up to about $8.00 a pop. I know when I was unable to develop my own I had a lab do it for about $5.00 a roll and I believe the was the hookup price. I understand we're still talking about less than $100, but if someone were sure they'd want to shoot a lot of IR or would make up for the cost of going digital over time, then I think digital is the way to go.
Nothing beats using film, sorry kids but that's my honest opinion. I have owned or at least used quite a few digital cameras/backs and found them to be all quite great, but there is something I can't do with digital ... use pyro developer and do platinum contact prints with 4x5, 5x7, 8x10, or 11x14 negatives. Then again, the market for these pieces of art is so small there's virtually no appreciation (read: money) for them.
I'm not trying to start a film/digital war, but having given consideration myself to converting a digital camera and considering the alternatives such as using film, I simply couldn't justify the cost over time.
OP: if you do decide to convert an old XT or whatever camera, I would recommend if you're at all capable, do it yourself. It seems rather straightforward (despite the fact I'm scared to do it), but if you save that money by doing it yourself you can get the "deep" B&W filter upgrade for another $50.00.
Initially I thought I might do it myself, but I don't own any soldering equipment, so I guess I'll have them do it. I want to stay with canon though, because I own a bunch of lenses already.