I tried calling the tax office of the county but the individual who answered the phone didn't seem to know and transferred me to a supervisor, for whom I left a VM but hadn't heard back yet.Thanks!

Maybe not always in your office.   

I'm keeping a Pittsburgh based return address on the postcards/letters, but I'd rather not have a giant collection of returned mailpieces pile up for me to collect on a regular basis.I've heard of an option where the post office can send you photos of your undeliverable mail and then discard it for you, but I can't seem to find anything about this service on the USPS site.

I do not need any support in the way of marketing, office or other overhead.

For example, could I sell a 5 million dollar office building and go buy a 10 million dollar portfolio of 100 SFHs that are individually deeded?

A parcel split in Florida typically involves filing a parcel split request form with the county property appraiser's office, and before you file it, you get the survey work done and find out if the relevant building or development department will support your request or not.

I have moved to the new home and work remote but plan to work from our office in San Francisco after remote.

Just make sure you work with a loan officer that know how to do it. 

Goto the Secretary of State’s website for corporations and LLC filing info, including the officers and mailing address. 3.

If its under that I would say have your banker or loan officer run a credit scenario simulator and see how to get the scores up the fastest.