if you're going to purchase a real portable raised dance floor then you'll be fine. if you're making your own ba sure to have a "floating floor" or some sort of padding between you and the concrete.
you don't want to injure yourself by dancing on a solid hard floor.
also... if you plan on leaving the floor on the cement you may want to put some sort of moisture barrier on the floor first before laying the floor. that way any condensation that develops wont hurt the wood.
Portable would be good if you aren't sure how long you want to have it set up there, but most portable floors have little built-in spring. Putting one right on concrete will give a very 'dead' result that will be really hard on your feet and legs.
I think you could probably buy flooring for substantially less than the cost of portable floor squares. You'll want a compliant support - criss-cross layers of wood, or some sort of rubber pad. And you probably want to look into moisture control - sealing the concrete, ventilating the space under the floor, or something.
You could looka t the technical specs for squash courts: they use a timber batten and and a rubber strip to provide resilience and spring to the floor. Any timber or wood product will be sensitive to moisture changes so allow for expansion at the edges of the floor. Putting a vapour barrier and insulation under the floor is a good idea - vapour barrier over the insulation will prevent condensation.
Of course this depends on your local climate: where are you?
I know one of our dance teachers whose parents installed a sprung floor across the entire upper floor of their house, so she does all her [Latin] dance teaching there. Another friend has also done the same with a section of the upper floor of their home for jazz training.
I've been thinking of doing something so my girlfriend and I can practice for an upcoming showcase. I have a (indoor/outdoor) carpeted basement, and was thinking of laying down some of the melamine coated particle board sheets available at Home Depot. Tough surface, similar "slide" to wood, and waterproof (though the edges will have to be sealed). Yeah, it's doctor's office white, but it's only ~ $1 per square foot Am thinking the carpet underneath will provide the "spring".
Any comments / opinions before I herniate myself hauling 100 lb sheets down the stairs?