My cat only had one kitten... I don't know what to do?

My cat Luna ran away awhile ago, but she's always been an indoor cat. We've seen her around the house for a few weeks, but I'm the only one she trusts and last night was the first time I've seen her. She came to me, and she was extremely skinny except her belly, so I knew she was pregnant. I set up a cardboard box with towels in it and fed her, but about an hour ago, she crawled under my dresser and I heard tiny meows. I removed the drawers, but didn't move her from under there because I heard that could jeopardize the health of the kittens. Only one came out, and she's nursing it right now, but I don't know if she should have more or not. Her stomach looks a little big still, and unfortunately since I live in a small town, the closest open vets office is 40 miles away. I don't have my license and my dad won't be home until tomorrow afternoon. I don't know what to do, because I've never experienced an animal having babies. This was the first cat we didn't fix because she was intended to be an indoor cat. The kitten seems healthy enough, and so does Luna. Could there be more kittens, or is this it? And does she absolutely need medical care? We don't have an extra $500 around to give her an ultrasound anyway... What should I do?