In the days when it was legal for a FDH to live-out, the rate was the basic salary (currently $3,440) + cost of lodgings, which is roughly $1,500/month.
Whether or not a local person would accept this salary is another question.
Another way of calculating would be to take the hourly rate of $50-60and multiply by the total no of hours you'd be asking the DH to work.
Sorry, can't comment on pros/cons; I hired my FDH after the rules changed and it was illegal to have them live-out.