If you were my client, with a score above 620, I'd get you 100% financing at about 6.25-6.5%, plus PMI.
Countrywide is very big. That doesn't necessarily make them good. The vast, vast majority of the loans in their portfolio were not created by them. They were bought from brokers and other banks.
Their retail loan officers aren't always that experienced, though they do at least get some training. And they're limited in their products.
Call a few brokers, one or two banks, and ask what rates they'd offer for a My Community Mortgage. That's almost guaranteed to be the product you are being offered by Countrywide. And unless you're combining that product with an interest-only period or a 40 year term, or both, you should not have to pay rates that high. Actually, if you did a 40 year term, interest-only for the first 10 years, you still shouldn't have a rate that high, but it'd be close (6.75-7.00?).
Get some competing offers. It is true that 660 is about the starting point for 80/20's, only because few banks offer 100% 2nd mortgages to anyone with a score under 660. The ones that do are likely to charge double-digit rates, and then PMI becomes the cheaper option anyway.
Countrywide isn't the only game in town. Not by a longshot. Worst-case, you'll find that they happened to be your best deal anyway. Unlikely, but possible. But at least you'll have confirmed it.
PS: You said you have $5000 saved. I don't know what kind of price range you are looking at, but you should also inquire about FHA financing. FHA requires a 3% downpayment. That $5K is 3% of about $167K. Another grand gets you eligible for a $200K purchase. FHA loan limits vary by county, but most areas can go as high as about $275K. So you're not far off. And FHA fixed rates today are about 6.00%, no minimum credit scores. Just one other option to ask about, see if it's right for you. FHA will allow a gift from family for your downpayment, so if you were only $1-2000 short, perhaps you could find some help from family?
And if you do that, actually under either option, make sure you structure your purchase offers to have the seller pay your closing costs.
10 years in mortgage banking