Joshua Thompson, yeah I probably made it sound more complicated than it is, in terms of the quality of the county's online records. Really, a lot of counties have very good online records at this point, so those that don't almost seem to be the exception and not the rule, but I'm talking about fundamental things like, do they have an online GIS system that allows you to look up properties by parcel ID, owner's name, etc., and see the location and basic attributes of the subject property, such as size, shape, zoning, etc.
Many people are very successful in states that don't publicize previous sales data for properties, but personally, up to this point, I prefer to work in states/counties where I can also see what at least the current owner of the property paid for it and when they bought it. Some counties' systems will show you the last several transactions' dates and prices.
Other than that, I'd like to be able to look up on a county website: what the property taxes are, and whether the current owner is current on their property taxes, or how much they owe currently if they're not current.
And yes, Seth's course has good content on all things related to selecting a market and doing research on properties (where some of the county tools come in).