A possible exception to this might be...

If you already do a lot of teaching work for them. If you are getting a fairly constant stream of contracts to teach this and that and the next thing... Then... Well... I actually know of a few people who have had a full time teaching workload with no research expectation with precisely this sort of work... They haven't completed their PhD's...

This is partly because it is much cheaper to hire them (since they don't have PhD's) than to hire someone who is properly qualified. It is also partly because the University doesn't have enough graduate students to share the teaching work out amongst its current graduate students.

I know a number of people who do this kind of work... If you have a 'portable partner'... Another source of income that can be relied apon, then it can work... You don't get health insurance or holiday pay or anything like that with this... Very much living from semester to semester with no job security at all...