I have a policy of no free work, for three reasons.
1 – Our time and creative effort has value – that should be compensated for.
2 – Free work encourages price/cost to be the sole mark of value for the design community, which devalues the experience, knowledge and abilities of the individual and encourages the lowest or cheapest to be the best, as opposed to the best fit or the appropriate solution.
3 – Would you work for free? I mean, seriously, would you?