More or less everyone needs a bed. Likewise, more or less everyone will eventually need to buy a bed for themselves, and that requires a fair bit of decision-making. What kind of decisions? We'll start with the one that will impact your living space the most significantly: deciding what size mattress to get. Not counting custom options, most manufacturers make six sizes of mattress: a twin sized mattress, a twin XL, a full, a queen size mattress, a king, and a california king. These vary in both length and width and are designed with a certain number of people in mind.
If you have a partner, a small child, and a dog, it might be a bad idea to go with the twin sized mattress or the twin XL. Other than that, your bedroom space should be your major concern. If you can, get the measurements of your room or the allotted space you have where you're planning to put the bed. Is there room for a bedside table or two? Are you leaving space to access outlets? Also, be sure you're not blocking any vents or doors from swinging open.