#1 ARV (after repair value): one bad estimate kills profit instantly—everything depends on resale price.
#2 Purchase price: smart investors follow the 70% rule to lock profit before buying.
#3 Rehab costs: typically 15–25% of project—underestimate this and margins disappear fast.
Holding + selling costs (6–8% fees, $50–150/day) quietly eat your deal alive.
Conclusion: profit = (buy low) + (control rehab) + (sell fast at strong ARV)