My old house was similar where there was a basement bedroom, bathroom, and its own separate entrance. There was also a tiny kitchen (basically just a refrigerator, an electric range/oven combo, and a sink) so the tenant never had to come upstairs. If there's space for it, and no regulations stopping you, I'd suggest adding a little kitchen in the basement if you can. A sink, a 40 amp circuit, and some inexpensive used appliances is just about all you need.
I just rented it to friends and overall the experience was fairly positive, and a good introduction to being a landlord.