The purpose of this study is to develop adaptive (AI) and micro-incentive (MI) interventions and test them against static (SI) and delayed-incentive (DI) interventions in a 4-arm randomized factorial trial to increase MVPA adoption and maintenance among inactive adults. Using neighborhood walkability and socioeconomic status, participants will be recruited from four neighborhood types: "high walkable/high SES," "high walkable/low SES," "low walkable/high SES," and "low walkable/low SES." We will evaluate synergistic or antagonistic effects of interventions and neighborhood factors on MVPA adoption by 12 months and maintenance by 24 months.