Paid ads aren't magical. They work when cost to acquire a customer is materially less than the customer's lifetime value. Before you spend a dollar, know the math.
Your LTV, divided by your target LTV:CAC ratio, is your allowable CAC. If LTV is $600 and you target 3:1, allowable CAC is $200. Any campaign whose CAC runs above that is losing money.
LTV:CAC of 4:1 over 5 years looks great on paper but kills cash flow. You need 4 years of capital to fund it. Payback period under 12 months is healthy; under 18 is acceptable; over 24 is a business model problem.
Early dollars of ad spend find the easiest customers (cheap CAC). Later dollars find harder ones (expensive CAC). At scale, blended CAC rises. What matters: the next dollar's CAC, not the average.
One tenant or product segment can have 10:1 LTV:CAC while another has 1.5:1. Blended looks fine; the mix hides a dying segment. Segment by acquisition channel, geography, product, cohort. Kill the losers.