What type of disability insurance policy likely to have he lowest premium for a given monthly payment?

Speaking very generally, an "any occupation" disability policy would have a lower premium than an "own occupation" policy. To collect under the first, one would have to be unable to perform any sort of job for which he/she is fit by virtue of education, experience or training. In contrast, you should be able to collect under the second type only if you are unable to perform the functions of the job that you had at the time of onset of disability. Therefore, since it is harder to qualify for benefits under the first type, the premium should be lower.

Another factor to consider is the "elimination period". This is sort of similar to a deductible in a property and casualty policy. It provides that the disability must last for a set period of time before benefits are payable. For example, there may be options to elect a 30, 60, 90 or 120 day elimination period.