Location Based SEO?

I have a pretty good idea for a way to make money off of a certain niche. I need to target specific areas however.

For example: "keyword dallas, tx" or "keyword ft worth, tx"

There's about 15 different locations that would be ideal for this (all in Texas)

Does the domain name HAVE to match the search query, or can I do SEO for
a different domain? I guess I would just have to have keywords on my pages, or maybe a "Areas of Service" page with the locations?

I know the idea will make pretty good long-term money, but only with the correct SEO done (and I'm not very good at that lol)

For example, can I have like: computer work in Dallas Tx (No, that's not it) and have ComputerRepairGuide.com?

I really only want this to target people in the northern part of Texas, but would like lots of organic traffic without a ton of useless traffic. I will only be able to make the money from the Northern Texas area.

Any ideas or tips? I'm in the planning stages right now. This will pretty much be my very first niche website.

I'm not as concerned about making fast money, as that will come later. I just want to make sure I'm targetting and getting traffic from the correct areas.