Aspiringprof,
I'm reading between the lines here in an attempt to answer your question.
First, you apply for a PhD program and then, depending on the level of support the program can/will provide you, they put you to work. This work is most likely to be in the form of a TA (teaching assistant) or RA (research assistant) role. Once you got far enough along in the program, you might/will be assigned a course(or more) that you teach. Depending on the university and the nature of the program, you might teach under close guidance of a professor or be assigned a course as "instructor of record."
One does not find a teaching job at a school and then get into that school's PhD program. Actually, I can think of a couple of scenarios where the horse-before-the-cart, adjunct-into-PhD-student scenario MIGHT apply, but I don't think you would likely fit that bill.
Which brings me to my next point --
Did you work prior to entering the MBA program? How much work experience do you have? What kind of responsibilities did you have?
It is possible to teach with an MBA, but one also needs a fair amount of professional experience. The major accrediting body for b-schools recognizes Academically Qualified (AQ) faculty and Professionally Qualified faculty (PQ). AQ faculty have doctorates and some level of other activity (research, consulting) within 5 year cycles. PQ faculty have Master's degrees and, to quote an AACSB (the accrediting body) document:
PQ status is normally granted to faculty members who, at the time of hiring, have professional and/or technical experience of significant duration and responsibilities.You can read more about these distinctions and expectations in this
AACSB document on faculty qualificationsI suspect that the reason you're being told you need to work part time or establish a business is because you are lacking the experience that would enable you to be designated as PQ. If that's the case, I'm not sure I agree with the "work part time" advice. What you need to do is find a full-time job, work for several years and do some adjuncting to dip your toes into the teaching side of things.
If you don't have work experience, theoretically, you could go straight from the MBA to the PhD, but in my experience on both sides of the hiring process for business professors, universities really like someone who has BOTH the PhD and work experience for their full-time faculty positions. There are those who go from UG to MBA to PhD without stopping off in the corporate world, but that's not everyone and I've seen those individuals viewed some suspicion in some places.
In some cases, very seasoned, career changing executives with MBAs are hired into full-time "executive in residence" or "clinical professor" type roles. I've also seen MBAs with lower level work experience hired as non-tenure track 4/4 fulltime lecturers who teach lower level undergraduate courses.
If you have the qualifications, you might be able to find "short term contract" teaching as an adjunct. This would happen in your local area as you become a known entity to the appropriate department chairs in your geographical area. (Make sure you read all the threads about what it means to be an adjunct.)
But moving cross country to find an adjuncting gig in a B-school (without work experience) which then might also absorb you into their PhD program? Not very likely. There's always the possibility that you can figure out how to be the exception, but such a trajectory would truly be an exception.
