Hi elbee, those cacti sold in bb stores are oftentimes small so, good for starting cacti lovers. They typically would grow bigger depending on their container or if you start planting them inground. But in containers, they stay smaller. They are rather slow growers, so it takes a good while before you need to repot. Handle them with care, always wear your gloves and if you do need to repot, you can wrap the plant with some newspaper so you can grab it safely as you change your container. Good luck and go for it!
Just remember, during winter, most of them are dormant, so water very, very sparingly, and really keep dry. They will resume active growing in Spring to Summer, then they will need watering, but again allow to dry. When you repot, always use containers with drainage holes and use cacti mix. I often add more pumice or perlite in my cacti mix, got to keep them as gritty as I can. They need fast draining media.