@Isaac El, you can do it anywhere. Section 8 is a federally funded program administered locally by a Public Housing Authority, so you may have different Public Housing Authorities to deal with depending on where you're at (I have 2 here in St. Louis that I work with, for instance).
While the general structure and rules are the same nationally, each PHA will have their own little differences, particularly when it comes to setting rents, timing for rent increase requests, and inspection frequency and difficulty.
It is not against federal housing laws not to take Section 8 but it can be against it not to based on a state or city law (in these cases, it is usually against the law to not take Section 8 AND it's against the law to do what I do, which is only take Section 8 because you can't discriminate based on "source of income").
As mentioned above, Section 8 rents are usually in line with market rents in B, C and D areas. They can even be a little above market rents, particularly in C and D areas. However, they will generally be below market rents in A areas because there is a ceiling on the amount that HUD will pay in rent, determined by your area's Fair Market Rent.
A lot of people end up hating Section 8 because they don't execute on it as well as they could. It takes meticulous tenant screening (which I would do anyway), solid processes & attention to detail to do well. I think it's worth it given the guaranteed rent and stability that it provides but it's not for everyone.
Also, there are great Section 8 tenants out there so my approach is to provide one of the nicest properties in the neighborhood - that way I attract a large number of applicants quickly and I can then pick the top one to live in my property.