I found bigger pockets by doing a google search on "best real estate books", which resulted in a comprehensive list that I've recently used. 

This is the point where the bundle of rights you have as the lessor/optioner of the property are so comprehensive and strong that in essence the ownership/control of the property has already transferred to you.The application of risk of loss passing is seen more in land contracts and lease to deed situations but given that option contracts can look very differently you'll want to pass it by your QI first.

There seems to be a list of "Real Properties Sold" on the OC website: http://ocgov.com/gov/pa/div/realproperty/auctions/...Does anyone know if this is comprehensive, or only a selection?

If so, how accurate,comprehensive, and of course reliable, are they?

@Mike Easton I would recommend "THE SELF DIRECTED IRA HANDBOOK" by @Mat Sorensen, which is comprehensive guide for self-directed investors.

Although not as comprehensive as MLS, Redfin is the best to look at the Comps. 

For the tenant screening report, it’s comprehensive and free.

I believe I understand the comprehensive due diligence performed once a contract is signed, but what do you look for before?

Its the most comprehensive data-set available and costs about 8 cents per downloaded record.

@Collin Goodwin Here are four options.Build a Mobile Home Park property management company from the ground up - cold call MHP owners (MHvillage.com has a comprehensive directory) and see if any of them are tired of managing their park (there will be plenty of people that say yes).