D.N.
It depends on what you are looking for. If you want one to use for your own child, a small one from Toys R Us is fine. It can be left up if you have it in th ehouse. Those water park type things can easily break and the sun can do a lot of damage. Also, absolutely NO SHOES allowed. My cousin in law bought one a while back and his son decided he wanted to wear his shoes. Lots of little holes. I know a woman that had small regular bounce house type. She left it inflated in her basement. Tip 1, use a vacuum to blow it up. She used a pump and it took forever. Tip 2, make sure you check the inflation every couple of days. Bouncing on it does cause pressure and deflation and Tip 3, buy insurance. Her house got a hole and she got a new one. But the policy only covered 1 replacement.
As for the electric bill , the smaller ones do not need the compressor like the big ones you can rent so no constant electricity use.