Lights
Lights are a vital part of good photography since photography is the art of light. You may have all the lights you'll ever need in your garage or shed. A halogen shop light works well as a main light. To spread the light evenly, hang a white sheet in front of the light. Get a smaller light to use as a fill light. A clip-on desk lamp can be used for a hair light. You'll need reflectors to create directional lighting. Consider an accordion car shade or a mirror for this purpose.
Props
Consider the type of studio pictures you'd like to offer. Christmas and spring time pictures are popular events that people memorialize with portraits. Visit your local thrift stores to build your inventory. A sled makes a great poser for one or two people, pair it with a wintry backdrop and small fir tree for a convincing holiday set. Old chests and vintage clothing make for an old timey look perfect for small children caught playing dress up. Peruse your own decor for things that can be repurposed for use in your studio.
Backdrops
Backdrops add a professional touch to your photography and you can be as creative as you want with them. For a basic black or white backdrop purchase a few yards of muslin fabric. It is available in several widths. Try your hand at creating you own scenic backdrop. Buy a few yards of fabric, draw or trace a picture on it then fill it in with acrylic paints. For the cost of a few yards of fabric and a few tubes of paint you can keep your studio stocked with unique backdrops.