Ferrets are extremly currious and playfull little creatures, they thrive off of being social and getting into whatever it is you don't want them into. A good rule of thumb to keep in mind when raising a healthy ferret is to give them a minimum of three to four hours out of their cage to play and investigate. How much of the house they get access to should be decided early on and measures taken to keep these rooms safe for your fuzzy kids. It is almost certain that you will miss something or not do as good of job at your ferret proofing as you had thought. Don't worry, ferrets have an uncanny way of showing you that you missed something by getting out of or into something.
Ferrets don't require you to buy them fancy toys, as they can easily be entertained with many household items such as grocery bags (use supervision). Other great ideas for ferret toys that can be found around the house are cardboard boxes, old blue jeans (they just love crawling through the pant legs) as well as t-shirts and socks to name a few.
There are also games that can be played with your ferrets like the towel ride where you walk backwards dragging a towel and laugh yourself silly as the ferrets chase and pounce on the towel as they hang on for a ride around the house. You will find many different ways to entertain your ferrets, and in playing games with them you will develope a fantastic bond.