Using a tanning bed even once could possibly give you cancer.
However it would be a rare chance that you would get cancer just from using a tanning bed only once.
Usually it takes several tanning sessions in a tanning bed over a few years or longer to develop cancer from the tanning bed.
Many people use tanning beds for years and never develop cancer such as skin cancer but some people develop cancer after a few tanning sessions in a tanning bed.
Tanning in a tanning bed is never really a healthy thing to do because the UV rays from the tanning bed are more dangerous to your skin than tanning in the natural sun.
Tanning in the natural sun gives you Vitamins which can be healthy and it's less harmful to tan naturally using the sunlight than to tan in a tanning bed.