Should I pay off debt or invest first?

Compare interest rates: pay off debt with rates above 7% before investing (credit cards, personal loans). For debt below 5% (most mortgages, federal student loans), invest simultaneously — historical market returns average 7-10%. For debt between 5-7%, do both: match your 401(k) employer contribution, then throw extra at debt. The math favors investing, but being debt-free has psychological value.