How much does it cost to advertise with Google & Yahoo search engines?

It depends firstly on your budget!!!
Go to Google advertising section and learn all important info.
If you have money for advertising in Google, do it, it really helps!

Google allows webmasters and AdWords users to determine the amount they want to pay for their ads. This is done through bidding. You bid for the keywords you want to associate with your ads. Basically, in terms of charging, Google gives you the flexibility of choice.

I use adwords, you can set an amount you want to spend per month and let google adjust the targets and ad displays. You can also track the words and remove the ones that are not generating clicks.

I set a recent amount for ads and it seems with the downfall of the USD, the price went up for good adwords just enough to notice.

do you have to pay an upfront fee with google?

Originally Posted by ShaunJ

do you have to pay an upfront fee with google?

No, it can be setup to bill you when you owed amount reaches a certain point. I have mine setup to deduct from my account twice a month.

It depends on you. How much budget you want to put. You can start on small amount if your just starting and invest in the keywords that brings traffic to your site most.

Because the process is loosely bid based, there isn't a straightforward answer to your question. However I think most people would agree Adwords is vastly superior to anything Yahoo has to offer.