I think the following is reasonable minimum:
2 years community school living at home.
2-3 years at a public university living in a dorm.
2 years community school living at home.
2-3 years at a public university living in a dorm.
Whether this is reasonable or not may depend on where you are in the country: some states have first rate community colleges and first rate public universities -- California comes to mind -- while others have very limited (and not so cheap) community colleges and mediocre state universities (no names), but many excellent private colleges and universities. In some states, again, California comes to mind, it's relatively easy (with a strong record) to transfer from a community college to the flagship university (e.g. University of California, just not Berkeley or UCLA anymore). In other states, most of your community college credits won't transfer and it's rare to transfer from a community college to a flagship public university.
Connecticut is an example of a state with limited community colleges, fourth-to-third rate state colleges, and a barely second tier flagship state university, but excellent private colleges (Wesleyan, Trinity, Connecticut College) and universities (Yale). The vast majority of high school graduates in even middle to upper middle class high schools in Connecticut go to private universities, colleges, or, if they go to public universities, out-of-state flagship universities (e.g. University of California, University of Michigan, University of Virginia, University of Wisconsin).