The Ricoh GR is a great little camera with an APC-S size sensor which makes it great for infrared photography because of the large sensor.
However, the second hand camera that I bought to convert was not in the best condition. There was fungus on internal hot mirror and was pretty beat up and scratched. The camera on the outside was pretty ugly but after removing the hot mirror and replacing it with clear glass. It turned out to be a pretty interesting camera for infrared photography. I also hot to glue a 37mm filter ring to the front of the lens in order to mount infrared filters.