Data sources by ZIP codes

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I'm looking for a data service that can give me the following data by ZIP code or County, in order of importance:

1. Gross average rental yields

2. Vacancy rates

3. Unemployment rates

4. Median family income

5. General demographic data

Numbers 3, 4, 5 are generally available for free, but I'm having trouble with 1 and 2.  I'm willing to pay, but I can't find a good service.  RealtyTrac seems to have this data in some of their quarterly reports, but I can't see where it is offered for sale generally.