For a 7yo, I'm with Outdoorsmen above. It's hard to beat a H&R/NEF Topper 410 Junior as a starter for squirrel. (or the Pardner/Pardner Compact) They can be found for about $120 for the basic and about $160 with a nice checkered walnut stock. I think it's a pretty good squirrel/rabbit gun for anyone. I have a Pardner in 20 ga that I bought as a college Freshman about 30 years ago for $42 at K-Mart. Still have it and my son started with it pheasant hunting until we got him an 870 combo. I've loaned that gun out to many a dad to get their sons/daughters started.

http://www.hr1871.com/Firearms/Shotg...rdnerYouth.asp