If the daughter adds her husband to her LLC, that makes it a multi-member LLC. That means the single member LLC would be closed permanently and forever, and a new, multi-member LLC would be opened and registered as such in FL.
Personally, the husband would probably be better off (and cheaper) starting his own single member LLC and registering it as such with the state. If you think you'd rather do otherwise, I would "HIGHLY" advise you seek the services of a tax attorney or other professional that is well versed in the matter.
In Florida, a multi-member LLC is required to file a 1065 tax return which is completely separate from the personal tax return. The 1065 return is due by March 15 each year, and the late penalty is $205 per member, per month.
Once the 1065 is completed and filed, a K-1 is issued to each partner which each partner will need to complete their personal 1040 tax return. It doesn't matter if the partner's are married to each other and filing a joint return either. So with a multi-member LLC you increase your filing requirements, as well as the cost of meeting those filing requirements.
