Large crack in basement floor should I buy

There are two guarantees with concrete, it will get hard and it will crack.

There are a few factors to look at, is it just cracked or is there separation and settling.

Does it extend through the foundation?

Are there any signs of settling in the walls or roof?

Where we live many houses built up until the 80's have foundation issues due to the clay they were built upon.

If we are looking at a house that has foundation issues we will always get a couple of foundation repair contractors to look at the house and give there input on the extent and price of repairs. By no means is this always a deal killer.