The HPI RS4 3 platform is reliable, popular, and a lot of fun to run and work on. The car looks to be in pretty good shape and he's offering a lot of helpful extra equipment, but the big question when it comes to nitro cars is the condition of the motor. I think my eyes starting bleeding trying to READ HIS CAPS LOCK RUN ON SENTENCE but I don't think he mentioned how many tanks/gallons the motor has seen. You might want to inquire with him on this.

Parts are very easy to come by, as HPI is well-known and widespread. You could expect something like 40-45 miles per hour out of the box with this car, I recall mine being pretty quick with the stock motor. The price you quoted is $140-170 USD, which I think is a good deal if the motor is in good shape considering all that is included.

*edit* You might also want to see if he's including the Rotostart starter. You'll need it to run the motor in the car without modifying it for a pullstart or starter box. Although now that I look at the first picture closely I believe I see it on the left edge of the box.