You can also keep historic analyses handy if you just use different tabs. 

I will state that historically San Diego has produced great ROI on RE investing. 

@Benjamin Cowles, because options exist historically so that an interested buyer can use a span of time to determine when and or if to purchase an asset from a flexible seller - not for someone to lock up a property for a period of time so they can find an actual buyer (unless you say that up front and the seller is willing).TICs are a manner in which title is held in real estate. 

Because even when they show you their fantastic historical returns, when you look at their fine print, it will/should ALWAYS have the disclaimer to the effect: "Past performance is no indicator of future results".ie.

Where are the best places to find historical market data such as changes in year-on-year median prices, or how many month's supply is there in a particular market, or how average days on market is changing from month to month or year to year?

Is there a formula you have that can let me know how much I should pay for a property based of the historic numbers?

Does anyone know of a good source to pull historic real estate sales data broken down (ideally) by house type, size, list price, sales price, days on market, etc.?

The prevalence of lead-based paint can vary by region, with the Northeast being at greater risk, with many more historical buildings and older homes, compared to other places.All of our properties are in the Pacific Northwest and were built prior to 1978.

I suspect 3.5% of a San Diego property will cost you less to enter than 20% OOS property (non owner occupied) that would be a good investment (note the real cheap OOS properties cannot be financed and therefore cost 100%).BTW San Diego financed buy and hold has historically produced better returns than any of those much cheaper OOS options. 

I want to know the specifics of dealing with historic or older homes in this area and if it is worth investing in them.