The Alpha 100 was the first Sony branded DSLR, introduced in 2006 after Sony took over the Minolta camera business. It is now found used on Ebay for around $100 with a basic lens.
By current standards, it lacks any video capability, has a sensor that needs lots of light, uses a slow processor that writes to an obsolescing card standards (compact flash) and has limited auto focus performance.
However, it also has in body stabilization and works with any lens from the extensive Sony and Minolta lines, so it remains an excellent tool which can still produce brilliant photos.
Any decent photography book will help you get more out of this heirloom.
A few links to reviews from the time it was introduced: