Unless There Was A Concern That It Would Be Obvious That A Lion Killed Him, Scar Could Have Killed Simba Himself Or At Least Stuck Around To make Sure The Hyenas Finish The Job.
Basically If Jafar Didn't Try To pull the give me the lamp and i'll help you up trick instead he should have helped aladdin up and when aladdin gave him the lamp then he could have killed him.
And Generally Cats Don't Know How To Spend Money And They Couldn't Talk To Humans Either So Edgar Could Have got Away With Buying Them Food But Spending It On Himself And Even Staying In A Different Room In The House.