A single stage RC LPF will attenuate according to how far down the slope of the curve. All "1st order" simple filters have a slope which is -6dB per octave (multiple of 2) or -20dB per decade (multiple of 10).
Consider 1% residual noise at 10kHz means -40 dB gain or 40 dB attenuation which is approximately 2 decades below 10kHz or 100Hz. Choosing this breakpoint is a tradeoff between noise suppression and DC response time during power up. However you might choose 60db down from 8V or 8mV which means 3 decades down from 10kHz or 10Hz.
The value of R depends on user requirements for load current and DC drop,which were not given. C is then is computed from f, and R and desired attenuation.
http://upload.wikimedia.org/wikipedia/commons/6/60/Butterworth_response.svg
There is no point where there is only DC in theory, as the filter just attenuates, but practical limits can be defined such that the DC response time is not excessively slow. Each application for filtering may be unique.