Proposed "free college" policies vary widely in design. The simplest set tuition to zero for everyone. More targeted approaches limit free tuition to those who demonstrate need through an application process. We experimentally test the effects of these two models on the schooling decisions of low-income students. An unconditional free tuition offer from a large public university substantially increases application and enrollment rates. A free tuition offer contingent on proof of need has a much smaller effect on application and none on enrollment. These results are consistent with students placing a high value on financial certainty when making schooling decisions.