Vacancy rates are available for major cities and zip codes, but vacancy rates do not tell you the whole story.

Having access to certain things on the MLS is something that a lot of investors look for, so I've offered to send expired listings, foreclosures, short sales, owner financed lists in whatever zip code or area that the investor is farming or marketing.

Section 10131.1(b)(1)(C) of the CA business and professions code says you need a license when:""The making of eight or more loans in a calendar year from the person's own funds to the public when those loans are held or resold and are secured directly or collaterally by a lien on residential real property consisting of a single dwelling unit in a condominium or cooperative or on any parcel containing only residential buildings if the total number of units on the parcel is four or less. ..."

Also fire safety or better: compliance with building code is a major obstacle.

Then I add the specifics for the property e.g for the recent one I added the lead paint disclosure, pamphlet, I added that it is a historic house so many of the historic features do not meet current code e.g. the banister height is lower than now required, pet addendum to identify the fish, dragon and one dog, etc. 

Lighting design and interfacing is one of my specialties, and I have a licensed electrician colleague who gives me a great price on certified installation (required by code).

Well, there used to be no limit; but what happened sometimes is that somebody would completely delete or alter what they had said, making replies seem like meaningless gibberish.

It also sounds like the Gov't program called Harp 1 and 2 where those home owners that were underwater on their homes and had difficulty paying their mortgage the rates would be altered thereby lowering the monthly payments.

Current codes require a certain thermal resistance that is not provided by many homes built several decades ago.

If they're hoarders, they'll have to make sure that it's not cluttered, as code enforcement would otherwise create a problem for you.