two routers

I’ve read several articles that suggest having 2 firewalls before entering your network with a DMZ between the two.

I have a couple questions about that.
1)I assume the 2 firewalls must assume different roles and filter different information, other they would just be unnecessary overhead.

2)What should the roles be?

3)What do I do I have don’t have anything to use as a DMZ? Do I siply point all traffic from firewall1 to firewall2?

4)Is it worth it to implement this scenario with only SOHO grade equipment?

TNX