I recommend contacting up to three attorneys with land-use experience in the Phoenix area and ask them this question. They will need more details about your property and the sought after re-zone to give you an estimate. It is too hard to give an estimate with such little information, because every jurisdiction and every re-zone is different. For instance, the cost and time involved go up significantly if your attorney needs to handle an appeal of the re-zone as opposed to just handling the permit work.
The first thing you need to do is look at what is around the property. If it is all residential -- and like your property, zoned residential -- it would be illegal in most states to rezone your lot to commercial use. That's called "spot zoning" and aside from the legality issues in Arizona, it's just plain bad zoning practice. If it isn't illegal in Arizona, it should be illegal. To put in it some perspective, how would you feel if somebody bought the lot next to your home and sought to rezone it to build a small retail building on it? Yep, I didn't think you'd be wild about the idea.
That said, you should indeed consult with a land-use lawyer or two -- or a professional city planner. Arizona is not exactly known for good land-use law. By 1955 only 3 cities in the state had adopted zoning codes (although that number has increased significantly in the past half century). It has been reported that Arizona "good-old boy favortism" has resulted in spot zoning. See pate 210 of "Politics and Policy in Arizona" edited by Zachary Alden Smith.
So while it might be possible to get away with spot zoning in Arizona, it is a lousy way to handle zoning and no responsible property owner should seek to engage in such a loathsome practice. I write this as both a land-use attorney and as a professional city planner.
The information provided in the question posed is not complete enough to provide accurate legal advice. More details are needed to really guide the questioner. My response is not intended to be taken as legal advice and does not establish an attorney-client relationship.
Why do you think this is a good location for your business, if it's all residential? it sounds like an iffy business proposition if nothing else. But it is highly unlikely to be permissible, and in most places would be an illegal use. Are you talking about something like a B and B? if so, that may be allowed in residential, but it would most likely require a use permit and the neighbors would have a chance to be heard at a public hearing.
Certainly check with a real estate lawyer and a business one too, to see if your potential venture even makes financial sense.
This response is not to be construed as establishing an attorney-client relationship, and provides general information on the subject at hand only.