Go for it, if the car is half-way decent on a test drive, it's worth taking home. The EF Civic models are old-school Honda-reliable in most cases, and get excellent mileage when driven to that aim.
I bought my Civic wagon for similar money, and in similar shape. It needed some work to pass emissions and new tires, but otherwise it's paying for itself. I average 40 MPG, and the wagon is taller, longer, rides higher, and weighs ~600 lbs. more than a CRX. I wanted a CRX all along, but the wagon was more practical. I'm still searching for a cheap CRX, and for $900 I'd probably buy the one you're looking at were it in my area.
