Should I rekey or change the locks when I buy a house?
Rekey, in almost every case. Rekeying changes the pins so every old key stops working and costs $30 to $80 per lock, or $120 to $350 for the whole house. Full replacement at $80 to $220 per lock only makes sense when hardware is worn, damaged, or you want restricted or smart locks. You have no idea how many copies of the old keys exist, so do it on settlement day. Tip: have every lock done in one visit and keyed alike so one key runs the house.
Full ranges, factors and sources: Locksmith Prices cost guide.