If you're looking for free sources, you've got more than a little bit of work ahead of you. You might find some luck contacting different county assessors and requesting their data, but there's no standard schema for this type of information so you're in for a lot of work. Some assessors provide free data, others require payment so YMMV.
If you have money to spend on your project, you could contact one of the various consolidated parcel providers such as Corelogic.