I already own a Comcast modem. So $40 is less then $100, it isn't less if you do $40 * 12. That's $480 a year. If I did pay the $100, it's $12 a month, that's $144 a year.
I could see how long Comcast will let me use it for free. I have no credit, so bad credit is better. I'll have credit then.