Yogurt is very easy to make. Do you use a culture you bought or just some yogurt you bought?
My roommate used to buy yogurt to feed his dogs, so I took a tablespoon and made a batch and showed that I could make it at home for about
1/10 the price. I used the oven. Just the heat of the oven light with a deck of cards propping the door open a crack gave me 110ish degrees.