Took all your advice and thought awhile and then it came to me: Since both businesses are linked via Filemaker, why even create a new db? Why not give the Realty agents access to the Property Management Leads file, but only those referred to them? Just add two fields: 1) Company assigned to and 2) Realty Co agent assigned.
So, question. How do I allow them the full functionality of the layout, but restrict them from seeing ANY leads from the PM side? A) Create a duplicate layout, but then associate all the fields to a new TO that is filtered just for the Realty Co? However, I think this breaks the scripts associated with some of the fields and the portal filter at the bottom, etc. B) A trick I learned: if I create a TO over in the Realty DB with the same name, then when I create a new layout and paste all the fields in, the fields will be linked to that TO; I don't have to relink them all. However, haven't done this with scripts. If I import all the scripts first BEFORE pasting the fields, will the script triggers work? Yet, any calc fields would not work, I think. C) Just create security in the Leads db where each Realty agent can only see their own leads. I could even create a dupe layout but leave it with the same TO, just remove fields I don't want them to see. Then, if they so choose, I could have a button that would import their Lead into their Contact table on the Realty side.
(Sorry to go on so long, but I think best when written out.)