Hourly Employee Housing Allowance

We have a part-time associate pastor who we are looking to convert to hourly (rather than PT salary). Currently, a portion of his salary is allocated as a housing allowance.

Is it possible to claim a HA while being an hourly employee?

If so, how would that work on a regular paycheck? Would the HA be “funded” first & then the rest of the pay toward the remaining hours? If so, what about a (rare, but possible) situation where he doesn’t work enough hours in a pay period to meet the HA level for that period first?

Converting to hourly makes sense for our circumstances in just about every way - except for this possible wrinkle. Any help would be greatly appreciated!